## Version Notes for Leptonica

##

Note: The following are highlights of the changes in each version. They are not a complete listing of the modifications.

    1.68   10 Mar 11
           Fixed windows issues with passing pointers across C-runtime boundaries
           when using dlls, by providing special functions (e.g., lept_fopen()).
           Proper version numbers are now set with automake.
           New utility (quadtree.c) for generating quadtree statistics.
           New utility (in colorspace.c) for conversions to and from YUV.
           Refactored functions for assembling image data for generating
           either PS or PDF images using g4, jpeg or flate encoding.
           Better tempfile names, using current time in microseconds.
           Functions for getting resolution from jpeg and png files.
           Use size_t throughout for reading and writing binary data.
           Deprecate arrayRead*() and arrayWrite() functions; replace in
           the library with l_binaryRead*() and l_binaryWrite().
           Better handling of colormap images for in-place rasterop and shear.
           New utility (bytearray.c) for parsing and handling binary data;
           used for generating PDF files.
           New utility (pdfio.c) for generating PDF files.
           Refactored regutils functions to make them simpler to use.
           Top-level deskew now works on any image.
           Added functions in utils.c for cross-platform development, mostly
           for functions that make and remove directories, copy, move
           and delete files, etc.  It should now be straightforward to write
           programs that will compile and run on windows.
           Reg tests have better printout; all give timings.
           New utility program: convertfilestopdf

    1.67   9 Nov 10
           Autoconf: now built with James Cuirot's config files that
             build the library and all 200 progs.
           New sudoku solver.  Just a game, but there are interesting aspects.
           Modified parseprotos.c to reject a type of "extern" decl.
           Add faster implementation for very small gray morphology
             operations (3x1, 1x3, 3x3).
           Eliminate warnings on recent gcc if you don't check return values
             from fread, fscanf, fgets, system, etc.
           Convolution: new functions for windowed variance and stdev; allow
             non-square kernel for windowed mean square.
           Put stdio.h and stdlib.h in alltypes.h, so they're not required
             in any .c files.
           Replace numaConvolve(), which is just a windowed mean, by
             windowed statistics functions (mean, mean square, variance).
           Generalize pixExtractOnLine() for arbitrary lines.
           Add pix interface to webp (webpio.c, webpiostub.c).  This is a
             new open source codec, based on the video codec vpx (webm).
           Serialization of FPix and DPix
           Interconversion between FPix and DPix
           Integer scaling of FPix and DPix; includes the last row and column.
           New convertfiles.c: depth conversion on files in a directory.
           Testing programs in prog:
               convolve_reg.c, numa_reg.c: expanded test set
               projection_reg.c (tests pixRowStats(), pixColumnStats())
               dewarptest.c: output ps and pdf files
               writemtiff.c: simple driver to write images to a single file

    1.66   3 Aug 10
           More tweaks for including (or not) bounding box hints for
             PS wrapping.  Default is to write b.b., but not in functions
             that wrap images as full pages (psio1.c, psio2.c)
           pix4.c split in two files, and added function to identify c.c.
             that are sufficiently similar in shape to rectangles (pix5.c)
           Modify 2 and 4 bit setters to clip the input value so that it can
             only affect the pixel requested (arrayaccess.c, arrayaccess,h)
           New pseudorandom sequence functions (numafunc1.c)
           Dewarping camera-based images using textlines (dewarp.c, prog/dewarp*)
           Geometrical function for aggregating overlapping bounding boxes.
           Programs to generate figures for book chapter "Document Image
             Applications" in "Mathematical Morphology: theory and applications"
             (see: http:/www.leptonica.org/najman-talbot-book-chapter.html)
             (prog/livre*.c)
           Functions that do affine and other operations in images with
             alpha blending at edges: pix*WithAlpha().  Also do this
             with a gamma/inverse-gamma wrapper to further reduce edge aliasing.
              (rotate.c, scale.c, projective.c, affine.c, bilinear.c,
               prog/alphaxform_reg.c)
           Improved color segmentation (fixed bugs; made faster)
           Higher order least square fits: quadratic, cubic, quartic. (pts.c)
           Various mods for otsu binarization and the *SplitDistribution*()
             functions (numafunc2.c, prog/otsutest2.c)
           Control sampling in convolution output (convolve.c, prog/fpix_reg.c)
           Morphological operations on numas (numafunc1.c, numafunc2.c,
             prog/numa_reg.c)
           Pix serialization wrapped so we can use pixRead(), etc on these
             files (spixio.c, readfile.c, writefile.c)
           Gif read/write to memory fixed (and cheated -- using files) (gifio.c)
           New fpix and dpix accessors; contour rendering on fpix (fpix1.c, fpix2.c)
           Various functions for linearly mapping colors and displaying arrays
             of colors (pix4.c, blend.c, prog/rankhisto_reg.c)
           Functions for getting approximate ranges of colors and color
             components in an image (pix4.c, colormap.c)
           Cleaned up windows platform and compiler defines and macros.

    1.65   5 Apr 10
           Added regression test utility functions for standardizing and
             automating construction and running of regression tests.  Makes the
             golden files when the 2nd arg to the reg test is 'generate'.
             (regutils.{c,h})
             Converted 22 reg tests in prog to use this; invoked with alltests_reg.
             Goal is to put all prog/*_reg.c into this format and put a set
             of golden files on the web.
           Small fixes in gifio for handling streams properly.
           New functions for shifting colors, hue invariant transforms, etc
             (blend.c)
           prog/dwamorph*.c: rename *1_reg.c to dwalineargen.c; others
             converted to standard reg tests.
           New rgb convolution functions.
           For PS output, write all images with a bounding box hint and with
             page numbers, which works for both embedded (e.g., in tex) and
             full page generated PS.  Once converted to pdf, this is fine
             in all situation.
           New functions for initialization and random insertion with pixcomp.
           For color quantization, make the lightest color white if sufficiently
             close; ditto for black (colorquant1.c, colorquant2.c).
           Rank binning of 8 bpp and rgb images (numafunc2.c, pix4.c)
           A function to rank colors by the intensity of the minimum comp (pix4.c)
           New pixRotateBinaryNice(), rotates 1 bpp pix in such a way that
             the shear lines aren't visible. (rotate.c)
           New pixSaveTiledWithText(), a convenience function to append text
             to images that are being tiled. (writefile.c)
           Stereoscopic warping functions and stereo pair functions (warper.c)
           Linear interpolated shear -- better than rasterop shear (shear.c)
           Option to use higher quality chroma (U,V) sampling in jpeg (jpegio.c)
           Rename Bmf --> L_Bmf.
           New tests in prog:
             alltests_reg.c alphaclean_reg.c, psio_reg.c, rankbin_reg.c,
             rankhisto_reg.c, warpertest.c

    1.64   3 Jan 10
           Easy setup for standard byte processing on 8 bpp pix (pix2.c)
           Evaluation of difference between similar images; test for
           similar images and (compare.c)
           Subpixel scaling, with color input and separate scale factors (pixconv.c)
           Fix tiff header reader to get correct format (tiffio.c)
           Enable pixDisplay() to work with i_view (windows) and with
             xzgv and xli as well as xv; allow application to choose
             which to use (writefile.c).
           Use a mask to specify regions that are changed by a morphological
             operation (morphapp.c).
           Improve the default sharpening for scaling (scale.c)
           Function to test for equivalence of file data (utils.c)
           Select and read image files with embedded index (readfile.c)
           Fix box size calculation in pixEmbedForRotation(); solution
             provided by Brent Sundheimer.
           New pixDisplayMultiple(), instead of calling gthumb directly; this
             is now set up to use i_view for windows.
           Changed criteria for determining if an image is color (colorcontent.c,
             colorquant{1,2}.c.
           Optional mode where the filename extension is automatically written
             to output image files; particularly useful for windows.
           Initialize boxa and pixa as full, with minimal placeholders.
           Get rank valued numbers and boxes in numa and boxa.
           Cute implementation for finding largest solid rectangle (maze.c)
           New median cut quantization for mixed (color/gray) images (colorquant2.c)
           Many changes to allow the library and applications be built easily
             in windows.  There is now a thorough windows readme, written by Tom
             Powers, for doing this.  The windows build information and
             project files are now in a new vs2008 directory.

    1.63   8 Nov 09
           Added pixScaleToGrayFast(), a faster version with very similar quality.
           Fixed scaleGrayLILow() to handle edge pixels more accurately
           Text processing:
             new text application (finditalic.c, prog/finditalic.c) for locating
               words in italic type style.
             Easier to add text to a pix using the bitmap font stored in
               the font directory; see, e.g., prog/writetxt_reg.c.
           Blending of 2 images with an alpha channel: pixBlendWithGrayMask()
           Fixed bug in color segmentation; it now (again) works properly.
           New utility (pixcomp.c) for handling compressed pix arrays in
              memory; new PixComp and PixaComp structs.
           Fast serialization of pix without compressing (pixSerializeToMemory
              and pixDeserializeFromMemory); required serialized colormaps
           FileI/O: new functions for reading file headers.
              PostScript generation modernized; split psio.c into psio1.c
                and psio2.c; added level 3 (flate) encoding.
              new functions for reading and writing multipage tiffs, for
                arbitrary input images.  For writing, compression is lossless
                (either g4 or zip)
              update all I/O stub files
           Miscellaneous: new pixaAddBorderGeneral(); new functions in pix3.c
              for counting fg pixels and summing 8 bpp pixels by column and row;
              new numaUniformSampling() for resampling with interpolation;
              subpixel scaling.
           New or improved regression tests in prog:
              extrema_reg, pixalloc_reg, blend2_reg, rotateorth_reg,
              ioformats_reg, colorseg_reg, pixcomp_reg, pixserial_reg,
              writetext_reg, psioseg_reg, subpixel_reg.
           Interface changes:
             findFileFormat() and findFileFormatBuffer(): now returns format
                 using input ptr.  The function return value is 0 if OK; 1 on error
             rename: pixThresholdPixels() --> pixThresholdPixelSum()

    1.62   26 Jul 09
           Expanded composite Dwa implementation as a sequence of operations,
           so that it now works beyond a size of 63.  It's typically about 2x
           faster than the composite rasterop implementation (with help
           from Ankur Jain).  Also use data transfer instead of data copy
           whenever possible.  Thorough tests with binmorph4_reg and binmorph5_reg.
           New functions in colorseg.c for masking and histogramming in HSV
           color space.
           Treat string constants rigorously as const char*, initializing
           to char[] if to be used as non-const, or in some cases casting
           to char*.  This avoids compiler warnings.
           Improved color quantization using existing colormap for octcubes
           and a new version for grayscale.  This will rigorously map most
           black and most white octcubes (rsp) to black and white
           if they exist in the colormap.
           Fast quantization to an existing colormap for color and grayscale.
           Fixed some bugs; e.g., in pixAffineSampled() for 1 bpp with
           L_BRING_IN_BLACK; reading and writing pnm for 2 and 4 bpp.
           In pngio.c, enable compile time control over these settings:
             converting 16 bpp --> 8 bpp on read
             removing alpha channel on read
             setting zlib compression on write
           For general scaling, allow sharpening to be optional, and provided
           faster sharpening operations.
           Improve support for 16 bpp grayscale.
           For scaleToGray* functions, reduce the width truncation.
           In psio.c, new functions for converting segmented page images
           (text and image) into level 2 PostScript.
           Removed all implicit casting to const char*.
           New custom pix memory allocator, designed for large pix whose
           memory needs to be reused many times.
           In xtractprotos, we now allow prepending an arbitrary string to
           each prototype.
           In environ.h, additions for MSVC to work with VC++6, including
           prototpye strings for dll import and export (thanks to Ray Smith).
           In colorseg.c, new functions for building HSV histograms, finding
           peaks, and generating masks based on the peaks.
           New or improved regression tests:
             pixalloc_reg, binmorph4_reg, binmorph5_reg, conversion_reg,
             scale_reg, cmapquant_reg,

    1.61   26 Apr 09
           New histo-based grayscale quantization: pixGrayQuantizeFromHisto(),
           that is used in new pixQuanitzeIfFewColorsMixed().
           Made final fix in pixBlockconv().  No underflows; no more overflows!
           More efficient rgb write with pnm.
           Add proto to jpegiostub.c, allowing proper use of the stubber.
           Fix several filter functions to use proper test on filter size; viz.,
             pixMinMaxTiles(), several functions in convolve.c.
           Redo shear implementation to handle arbitrary angles, to handle
             colormapped images, and to avoid the singularity at pi/2.
           Removed both static vars from pixSaveTiled().
           Generalized pixRotate() to handle colormapped images, and to use
             pixRotateBySampling() in place of the removed pixRotateEuclidean().
           New skew finder for full angle range, pixFindSkewOrthogonalRange().
           For skew detection, now allow shear about image center as well as
             about the UL corner.
           New rotation reg tests: rotate1_reg.c and rotate2_reg.c.
           Better serialization format for boxaa; introduce new version numbers
             for boxaa, pixa, and boxa, as required.
           Proper init in boxGetGeometry(), boxaGetBoxGeometry(), and the
             accessors in sel1.c and kernel.c.
           Improved Numa functions in numafunc1.c and numafunc2.c; in
             particular, numaMakeHistogramAuto() and numaGetStatsUsingHistogram().
             With all histo generators, make sure the start and binsize params
             are properly set and are used.
             Interface change: Use these parameters implicitly in
             numaHistogramGetRankFromVal() and numaHistogramGetValFromRank().
           Interface change to ptaGetLinearLSF(): add 1 optional parameter.
           In several pixaDisplay*() functions, handle colormaps properly.
           pixafunc.c split to pixafunc1.c and pixafunc2.c.
             New connected component selections and options in pixaSort.
           Patch from Tony Dovgal for reading tiff rgba files.
           Added new logical operation options for numas.
           New pixConvertRGBToGrayMinMax() that chooses min or max of 3 components.
           Computation of pixelwise aligned stats between multiple images
             of the same size (e.g., video), in pix4.c.
           Very fast binsort implemented for boxa and pixa.
           Cleanup and rename stack, queue, heap and ptra functions:
             all structs and typedefs start with "L_"
             all functions start with "l"
           Sel creation for crosses and T junctions.
           New thresholding operations to binary; split out from adaptmap.c
             into binarize.c.
           Implementation of sauvola binarization, including use of pixtiling.
           Added composite parallel union and intersection morphological operations.
           Small changes to scaling and rotation to improve accuracy; only
             visible on very tiny, symmetric images.
           Implemented DPix (double precision data); useful for the mean
             square accumulator for sauvola binarization.
           New fast hybrid grayscale seedfill, in addition to the interative
             version (contributed by Ankur Jain).
           New or improved regression tests:
             rotate1_reg, rotate2_reg, shear_reg, numa_reg, skew_reg,
             ptra1_reg, ptra2_reg, paint_reg, smallpix_reg, pta_reg,
             pixmem_reg, binarize_reg, grayfill_reg.

    1.60   19 Jan 09
           Fixed bug in pixBlockconv(), introduced in 1.59, that causes
           overflow when convolving with an image that has white (255)
           at the edges.  [quickly found by Dave Bryan]
           Include function to display freetype fonts in a pix.
           The files freetype.c and freetype.h are in the distribution, but are not
           yet linked into the library.  This is contributed by Tony Dovgal,
           and this version works only for MSVC.
           Found that the problems with binary compression in giflib are fixed
           with giflib 4.1.6.

    1.59   11 Jan 09
           Lots of changes since 1.58.
           New files: affinecompose.c, ptra.c, warper.c, watershed.{h,c}.
              Split: boxfunc.c --> (boxfunc1.c, boxfunc2.c, boxfunc3.c)
           Improved connected component filtering, with logical functions
           applied to indicator arrays (pix4.c, pixafunc.c, numafunc1.c).
           Function to determine if an image can be quantized nicely with
           only a few colors (colorcontent.c, pixconv.c).
           New gray seed-filling functions (seedfill.c, seedfilllow.c).
           Fixed bugs in tophats and hdome, due to misuse of pixSubtractGray()
           (morphapp.c).
           New function for improving contrast (adaptmap.c)
           Watershed transform (still slightly buggy) (watershed.c,h).
           Fast random access into a pix using line pointers (pix1.c, arrayaccess.*)
           Conversions of colormaps from gray to color and v.v. (colormap.c)
           Seedfill function that applies an upper limit to the fill
           distance (seedfill.c)
           New function for warping images with random harmonic distortion
           (with help from Tony Dovgal).
           New generic ptr array utility: all O(1) functions of a stack plus
           random replace, insert and delete (ptra.c).
           Simple functions for colorizing a grayscale image with an arbitrary
           color (pixconv.c, colormap.c)
           Flexible affine transforms (translation, scale, rotation) on pta
           and boxa (affinecompose.c).
           Clipping of foreground (both exact and approximate) starting from
           within a rectangular region of the image (pix4.c)
           Blending a colored rectangle over an image (pix2.c, boxfunc3.c)
           Generation of rectangle covering of mask components (boxfunc3.c).
           Block convolution using tiles (for very large images)  (convolve.c)
           New or improved regression tests in prog:
              locminmax_reg, lowaccess_reg, grayfill_reg, adaptnorm_reg,
              xformbox_reg, warper_reg, cmapquant_reg, compfilter_reg,
              splitcomp_reg, affine_reg, bilinear_reg, projective_reg
           Acknowledgments:
           (1) Big thanks to Tony Dovgal for helping with the warping
               (e.g. for captcha).  Tony also provided an implementation that
               allows rendering truetype fonts into a Pix on windows.
               This is not yet incorporated, because it opens a huge
               "can of worms," which is OK if you're going fishing but
               maybe not if you're trying to support leptonica on many platforms.
               TBD.
           (2) David Shao provided a libtools build system that includes
               building the prog directory!  I believe this will work, but it
               is is not yet included because of problems I continue to have
               with macros in version 2.61 of gnu libtools.
           (3) Steve Rogers is working on a MSVC build for the prog directory.
               I hope to have this available for 1.60.

    1.58   27 Sept 08
           Added serialization for numaa.
           New octree quantizer pixOctreeQuantByPopulation(), that uses a
           mixture of level2 and level4 octcubes.  Renamed many functions
           in colorquant1.c, and arranged/documented them more carefully.
           Revised documentation in leptonica.org/papers/colorquant.pdf.
           Simplified customization for I/O libraries and fmemopen() in environ.h.
           Fixed bugs in colormap.c, viewfiles.c, pixarith.c.
           Verified Adam Langley's jbig2enc (encoding jbig2 and generating pdf from
           these encoded files) works properly with the current version -- see
           Section 24 of README.html for usage and build hints.
           New separable convolution; let pixConvolve() take 8, 16 and 32 bpp input.
           New floating pt pix (FPix) utility, which allows convolution and
           arithmetic operations on FPix; also interconversion to Pix.
           Ability to read headers on multipage tiff.
           More robust updown text detection in flipdetect.c.
           Use of sharpening to improve scaling when the scale factor is near 1.0.
           See prog/fpix_reg.c for regression test and usage.
           See prog/blend_reg.c for blending regression test, with new functions.

    1.57   13 Jul 08
           New Debian distribution for 1.57 (thanks to Jeff Breidenbach).
           Improved the Otsu-type approach for finding a binarization threshold,
           by choosing the min in the histogram subject to constraints
           (numafunc2.c, adaptmap.c)
           New function pixSeedspread() in seedfill.c, similar to a voronoi tiling,
           that is used for adaptive thresholding in pixThresholdSpreadNorm().
           In the process, fixed a small bug in pixDistanceFunction().
           (The approach was suggested by Ray Smith, and uses the fast
           Vincent distance function method to expand each seed.)
           Generalized the functions in kernel.c to use float weights
           for general convolution (Version 2 for kernel), and added
           gaussian kernel generation.
           Put all jpeg header functions into jpegio.c, where they belong.
           Fixed bugs in pixaInsertPix() and pixaRemovePix().
           Added read/write serialization for Numaa.
           New functions for comparing two images using bounding boxes (classapp.c).

    1.56   12 May 08
           Added several new 1d barcode decoders.  The functional interface
           is still in flux.
           Autoconf!   To get this working, it was necessary to: determine and
           set the endian flag; select which libraries are to be linked;
           determine if stream-based memory I/O is enabled.
           This required a major cleanup of the include files, minimizing
           dependencies on external library header files, and getting everything
           to work with both autoconf (HAVE_CONFIG_H) and the old
           customized makefile.  Customization is now all in environ.h.
           pixSaveTiled(): a new way to display tiled images.
           pixtiling.c: interface for splitting an image into a set of
           overlapping tiles, using mirrored borders for tiles touching the
           image boundary.
           pixBlendHardLight(): new blending mode with nice visual effects.
           pixColorFraction(): determines extent of color in image
           Both octree and median-cut color quantization check first if
           image is essentially grayscale; improvements to both algorithms.
           box*TransformOrdered(): general sequence of linear transforms.
           colorquant_reg.c, xformbox_reg.c, hardlight_reg.c: new regr tests.

    1.55   16 Mar 08
           New functions for combining two images arbitrarily through a mask,
           including mirrored tiling (pix3.c)
           Modify pixSetMasked*() to work on all images (pix3.c)
           New functions for extracting masked regions such as pixClipMasked()
           (pix3.c) and pixMaskConnComp() and pixMaskBoxa() (boxfunc.c).
           New functions to separate fg from bg (pix3.c), one of which is supported
           by numaSplitDistribution (numafunc.c).
           Modify sobel edge detector to take another parameter (edge.c)
           Support for 4 bpp cmyk color space in jpeg (jpegio.c)
           Modified median cut color quantization (colorquant2.c)
           Renamed colorquant.c (for octree quant) --> colorquant1.c.
           Absorbed conncomp.h and colorquant.h into specific files that
           depend on them (colorquant1.c, conncomp.c, pix.h)
           General convolution with utility for building kernels
           (convolve.c, kernel.c)
           Initial implementation of 1D barcode reader.  So far, we just have the
           signal processing to locate barcodes on a page, deskew them, and
           find the bar widths, along with decoders for two formats.
           (readbarcode.*, prog/barcodetest.c)
           Made the default to stub out read/write for non-tiff image formats
           to memory; it doesn't work on Macs & they were complaining (*io.c)
           Include MSVC project files for building leptonlib under
           windows (leptonlib.*)

    1.54   21 Jan 08
           Histogram equalization (enhance.c).
           New functions for pixaa: serialization (r/w), creation
           from pixa, and a tiled/scaled display into a pixa (pixabasic.c,
           pixafunc.c).
           Read/write of tiff to memory (instead of a file, using
           the TIFFClientOpen() callback interface), contributed by Adam
           Langley (tiffio.c, testing in prog/ioformats_reg).
           Improved image statistics functions, both over tiles and
           through a mask over the entire image.  Added standard deviation
           and variance; enable statistics for rgb and colormapped images,
           in addition to 8 bpp grayscale (pix3.c).  New function to
           extract rgb components from a colormapped image (pix2.c).
           Fix pixWriteStringPS() to work with all depths and colormap (psio.c)
           Enable all non-tiff formats to also write and read to/from memory (*io.c)
           Added support for read/write to gif, contributed by Tony Dovgal
           (gifio.c, gifiostub.c, imageio.h).  See Makefile for instructions
           on enabling this.

    1.53   29 Dec 07
           Add 4th arg to pixDistanceFunction() to specify b.c.,
           and fixed output to 16 bpp grayscale pix. (seedfill*.c)
           New un-normalized block grayscale convolution (convolve.c)
           Fixed bug in getLogBase2(), so that pixMaxDynamicRange() works
           properly.  This is useful for displaying a 16 bpp pix as
           8 bpp (pixarith.c).  New function for getting rank val for
           rgb over a region specified by a mask (pix3.c).  New function
           for extremem values of rgb colormap (colormap.c).  New
           function pixGlobalNormNoSatRGB(), a variant of pixGlobalNormRGB()
           that prevents saturation for any component above a specified
           rank value (adaptmap.c).  Added mechanism for memory
           management of pix (pix1.c).  Added selective morphology by
           region given by a mask (morphapp.c).  Fixed prototype extracdtion
           to work properly with function prototypes as args; released
           version 1.2 of xtractprotos (parseprotos.c, xtractprotos.c).
           Add a boxa field for pixaa, along with serialization (pixabasic.c),
           and modified display of pixaa to include this (pixafunc.c).
           Coalesced the version numbers for pixa, pixaa, boxa, and boxaa
           serialization (pix.h).
           New progs: modifyhuesat displays modified versions on a grid;
           textlinemask shows simple methods for extracting textline masks.

    1.52   25 Nov 07
           Implemented Breuel's whitespace partitioning algorithm (partition.c).
           Generalized pixColorMagnitude() to allow different methods
           for computing the color amount of a pixel (colorcontent.c).
           New methods for computing overlap of boxes (boxfunc.c).
           New methods for painting (solid) and drawing (outline) of boxes,
           replacing boxaDisplay() with pixDrawBoxa*() and pixPaintBoxa*()
           (pix2.c, boxfunc.c).
           Ray Smith fixed bug in the distance function (seedfilllow.c).
           For pixConvertTo1() and pixConvertTo8(), treat input pixs as a
           const and never return a clone or altered cmap (pixconv.c).
           Make pixGlobalNormalRGB() crash-proof (adaptmap.c).
           Tony Dovgal added ability to read jpeg comment (jpegio.c).

    1.51   21 Oct 07
           Improved histogramming of gray and color images (pix3.c)
           Histogram statistics (numafunc.c).  Better handling of tiff
           formats, testing rle and packbits output and improving
           level 2 postscript conversion efficiency (readfile.c, psio.c).
           Test program for r/w and display of Sels (prog/seliotest.c).
           Use endiantest to determine automatically which flags to set
           when compiling for big- or little-endians (endiantest.c)
           Compute a color magnitude for each rgb pixel (colorcontent.c).
           Allow separate modification of hue and saturation (enhance.c).
           Global transform of color image for arbitrary white point (adaptmap.c).

    1.50   07 Oct 07
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           NOTE CAREFULLY: The  image format enum in imageio.h has
           changed.  This is an ABI change, and it requires
           recompilation of the library.
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           Suggestions by David Bryan again resulted in several changes,
           including improvements to the dwa generating functions and interfaces.
           Major improvements for dwa code generation, including an
           optional filename for the output code, adding function prototypes
           to the code so it can easily be linked outside the library.
           Addition of 2-way composable dwa functions for bricks, with
           code addition to the library, and a new interpreter for dwa
           composable brick sequences  (fmorphauto.c, fhmtauto.c,
           morphtemplate1.c, hmttemplate1.c, morphdwa.c, dwacomb*.2.c, morphseq.c)
           Exhaustively tested in six programs (prog/binmorph*_reg,
           prog/dwamorph*_reg).
           New input modes for Sels, from both color bitmap editors
           and a simple file format (sel1.c).
           Better Sel generation functions in sel2.c, including combs for
           composable brick operations and linear bricks for comparison.
           Removed unnecessary copies for more efficient border add'n & removal.
           Added RLE basline enc/dec for tiff.
           Binary morphology documentation on the web page updated for these
           changes/additions.
           William Rucklidge unrolled inner loops and added LUTs to
           speed up several more functions, including correlation
           (correlscore.c), centroid calculation (morphapp.c),
           2x linear interp grayscale scanning (scalelow.c),
           thresholding to binary (grayquantlow.c), and removal
           of colormaps to gray (pixconv.c).

    1.49   23 Sep 07
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           NOTE CAREFULLY: The  image format enum in imageio.h has
           changed.  This is an ABI change, and it requires
           recompilation of the library.
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           Suggestions by David Bryan resulted in several changes.
           pixUnpackBinary() unpacks to all depths.
           Can now write and read tiff in LZW and ZIP (gzip) formats.
           These, like uncompressed tiff, work on all bit depths.
           Also enabled pnm 16 bpp r/w, both non-ascii and ascii.
           ioFormatTest() now has better coverage and clarity; this is
           used in prog/ioformats_reg.c.
           Rewrite of morphautogen code to implement opening and closing atomically.
           Cleaner interaction with new text templates (fmorphauto.c,
           fhmtauto.c, sarray.c, *template*.txt,).
           More regression testing (e.g., binmorph1_reg.c, binmorph3_reg.c).

    1.48   30 Aug 07
           William Rucklidge sped up pixCorrelationScore() by in-lining
           all bit operations (jbclass.c).
           Generalized rank filtering from 8 bpp to color (rank.c).
           Fixed many functions that take a dest pix so that they don't fail if
           the dimensions or depth are not consistent with the src pix.
           The underlying change for this is to pixCopy() (pix1.c).
           Improved display of Sel as a pix; added selaDisplayInPix() to
           display all Sels in a Sela, orthogonal rotations of Sels (sel1.c).
           New functions for thinning and thickening while preserving connectivity
           and avoiding both free end erosion and dendritic cruft (ccthin.c,
           prog/ccthin1_reg.c, prog/ccthin2_reg.c).
           New function pixaDisplayTiledInRows() for compactly tiling pix
           in a pixa, plus documentation of different existing methods. (pixafunc.c)

    1.47   22 Jul 07
           New brick rank order filter (rank.c, prog/ranktest.c, prog/rank_reg.c).
           Use mirror reflection b.c. to avoid special processing at
           boundaries (pix2.c).  Simple sobel edge detector (edge.c).
           Utility for assempling level 2 compressed images in PostScript
           (psio.c, prog/convertfilestops.c).  Enable read/write of 16 bpp,
           grayscale tiff (tiffio.c, pix2.c).
           New function for finding the number of c.c., which is a bit
             faster than finding the b.b. or the component images (conncomp.c)
           New functions for finding local extrema in grayscale image (seedfill.c)

    1.46   28 Jun 07
           Added interpreted mode for color morphology (morphseq.c).
           In functions, make effort to consistently do early initialization
           of ptrs to objects returned on the heap.  This is to try to
           avoid letting functions return uninitialized objects, even if
           the return early because of bad input.
           Split pixa.c into 2 files; revised the component filtering
           in both pixafunc.c and boxfunc.c.  Added component filtering
           for "thin" components.
           Added subsampling functions for numa and pta.
           Word segmentation now works at both full and half resolution.
           Better methods for displaying and tiling (for debugging),
           using pixDisplayWrite(), pixaReadFiles() and pixaDisplayTiledAndScaled().

    1.45   27 May 07
           Further improvements of orientation and mirror flip detection
           (flipdetect.c).  Added 2x rank downscaling and general integer
           replicative expansion (scale.c).  Simplified interface for
           averaging, and included tiled averaging, which is yet another
           integer reduction scaling function (pix3.c).

    1.44   1 May 07
           Split pix2.c into (pix2.c, pix3.c), with basic housekeeping
           functions (e.g., ops on borders, padding) in pix2.c.
           Split numarray.c into (numabasic.c, numafunc.c), with
           constructors and accessors in numabasic.c.  Added a number
           of histogram, rank value and interpolation functions to numafunc.c.
           Add rms and rank difference comparison functions (compare.c).
           Separated orientation and mirror flip detection; fixed the latter
           (flipdetect.c).

    1.43   24 Mar 07
           New and fixed functions for handling word boxes (classapp.c)
           More consistent use of L_* flags (e.g., sarray.h, morph.h)
           Morphology on color images (gray ops on each component) (colormorph.c)
           New methods for generating sels; we now have five methods in
           sel1.c and 3 others in selgen.c.  Also a function that
           displays Sels as an image, for use in documentation (sel1.c)
           New high-level converters, such as pixConvertTo8(), pixConvertTo32(),
            pixConvertLossless()   (pixconv.c)
           Identify regression tests, and rename them as prog/*_reg.c.
           Complete revision of plotting package (gplot.c)
           New functions for comparing pix (compare.c)
           New morph application functions, such as the ability to run a
           morph sequence separately on selected c.c. in an image, and
           a fast, quasi-tophat function (morphapp.c)
           Cleanup and new interfaces to border representations of c.c. (ccbord.c)
           Page segmentation application (pageseg.c)
           Better serialization with version control for all major structs.
           Morphological brick operations with 2-way composite sels (morph.c)

    1.42   26 Dec 06
           New sorting functions, including 2-d sorting, for boxa and pixa,
           and functions that sort by index (e.g., pixa --> pixa and
           for 2d, pixa --> pixaa; ditto for boxa).
           New accessors for pix dimensions.  A new strtokSafe() to
           substitute for strtok_r (utils.c).
           Page flip detection, using both rasterop and dwa morphology
           (flipdetect.c), with dwa generation (fliphmtgen.c) and testing
           (prog/fliptest.c).
           Increased basic sels from 42 to 52 (sel2.c).
           Better high-level interfaces for binary morphology with
           brick (separable) sels, both for rasterop (morph.c) and for
           dwa (morphdwa.c); fully tested for both asymmetric and
           symmetric b.c. (prog/morphtest3.c).  Faster area mapping
           reduction for power-of-2 scaling.

    1.41   5 Nov 06
           Simplified morph enums, removing all unused ones (morph.h).
           Added new high-level interfaces for adaptive mapping (adaptmap.c).
           New method to extract color content of images (colorcontent.c).
           New method to generate sels from text strings, and to identify
           roman text that is not properly oriented (thanks to Adam Langley).
           Fast grayscale min/max (rank) scale reduction by integer factors.
           New accessors for box and sel, that should be used when possible.
           Thresholding grayscale mask by bandpass (grayquant.c).
           Use of strtok_r() for thread safety.

    1.40   15 Oct 06
           Fixed xtractprotos for cygwin.  Minor fixes and improved documentation
           (baseline.c, conncomp.c, pix2.c, morphseq.c, pts.c, numarray.c,
           utils.c, skew.c).  Add ability to quantize an rgb image to a
           specified colormap (colorquant.c); tested in prog/cmapquanttest.c.
           Modifications to allow conditional compilation on MS VC++,
           and to allow I/O calls to be stubbed out (new files: *iostub.c,
           zlibmemstub.c, pstdint.h, arrayaccess.h.ms60)

    1.39   31 Aug 06
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           NOTE CAREFULLY:  There has been an interface change to make
           affine, bilinear and projective transforms more general.
           The implementation has been changed to allow them to handle
           all image types and to make them faster (esp. with both sampled
           and interpolated mapping on color images).
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           Added prog/Makefile.mingw to build executables.  This is still
           in a relatively raw state.  It is necessary to download
           gnuwin32 packages for 4 libraries (jpeg, png, zlib, tiff)
           to link with leptonlib and the main, and I still have not
           been able to build static executables (they require jpeg2b.dll, etc.).

    1.38   8 Aug 06
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           NOTE CAREFULLY: There has been an interface change to both
           simplify and generalize the grayscale morphology operations:
               pixErodeGray(), pixDilateGray(), pixOpenGray(),
    	   pixCloseGray(), pixTophat() and pixMorphGradient().
           The prototypes are not changed; old code will compile, but
           it will be wrong!  The old interface had a size and a type
           (horizontal, vertical, square).  The new interface takes
           horizontal and vertical Sel dimensions.
           |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
           For cross-compilation to make windows programs, you can use
           src/Makefile.mingw to make a windows version of the library.
           6x scale-to-gray function donated by Alberto Accomazzi.
           Interpreter added for sequence of grayscale morphological
           operations, including the tophat (morphseq.c).
           Pixacc container added to simplify the interface
           for accumulator arithmetic using Pix.
           Removed fmorph.c and fmorphlow.c from the library.  These are
           very limited and were deprecated in favor of fmorphauto(), which
           autogens the code from (nearly) any Sel.
           Fixed some of the gray morphology operations, which had errors
           on the boundary.  All gray morph ops should now be rigorously
           OK (graymorph.c).  For testing of graymorph dualities, the
           the graymorph interpreter, etc., see prog/morphgraytest.c.

    1.37   10 Jul 06
           [After v.36 was released, Jeff Breidenbach built a Debian
           distribution of Leptonica based on v.36, and you can now get Leptonica
           as a Debian package.  Use "apt-cache search leptonica" to see
           what is available.]  The libraries are now combined into a single
           library (liblept.a, liblept.so) and the function prototypes are
           also in a single file (leptprotos.h).  cextract was found not
           to work on recent versions of linux that support 64 bit data types,
           and it is no longer distributed with leptonica.  Instead, I wrote
           a prototype extractor in leptonica (xtractprotos).  When you
           'make allprotos', it now uses this program.  The shared libraries
           now have major and minor numbers corresponding to the version.

    1.36   17 Jun 06
           Line graphics generation (graphics.c) reorganized; separated out pta
           generation from rendering.  Can now render with alpha blending.
           Examples of use are given in prog/graphicstest.c.
           Sort functions for basic geometrical objects now have the option
           of returning a numa giving the sort order on the original array.
           The pixa sort can sort with either clones or copies of the pix.

    1.35   21 May 06
           The efficiency of the multipage jbig unsupervised classifier is
           significantly improved due to a NumaHash struture implemented
           by Adam Langley.  Functions for computing runlength in 1 bpp
           images have been added.

    1.34   7 May 06
           Completely rewrote the jbig unsupervised classifier.
           It now works on multiple pages, and is more accurate in performing
           visually lossless substitutions.  You can classify by connected
           components, characters, or words.  The old data structures
           and interfaces have been removed.  New unpackers from 1 to 2 and
           1 to 4 bpp, with and without colormaps in the dest.

    1.33   18 Mar 06
           Generalized color snap to have different src and target colors,
           and to include colormaps (blend.c).  Distribute into root directory
           that specifies the version number (e.g., 1.33).  Add color
           space conversion between rgb and hsv.  Re-bundle thresholding
           code from (binarize*.c, dibitize*.c) to grayquant*.c.
           pixThreshold8() now also quantizes 8 bpp --> 8 bpp.
           High-level pixRotate() that optionally expands image sufficiently
           so that no pixels are lost in any sequence of rotations (rotate.c).
           Generalize shear to specify color of pixels brought in, including
           for in-place operation (shear.c, rotateshear.c).  Faster version of
           color rotation by area mapping, both about center and about UL corner.
           You can now use the standard color rotator (pixRotateAM) and get
           nearly the same speed as with the "Fast" one.

    1.32   4 Feb 06
           Ability to specify a sequence of binary morphological
           (& binary reduction/expansion) operations in a single
           function (morphseq.c).  Fast downscaling combined with conversion
           from rbg to gray and to binary (scale.c).  Utility for
           segmenting images by color (colorseg.c).

    1.31   7 Jan 06
           Remove more complicated functions that threshold to 2 bpp,
           retaining the simplest interface.  Retest all thresholding and
           dithering.  Add "ascii" write of PNM.  Improve graphics writing
           of lines; generalize to colormaps.  New colorization functions
           (paintcmap.c, blend.c).

    1.30   22 Dec 05
           Remove most instances of fprintf(stderr, ...), except within
           DEBUG or encapsulated in error, warning or info macros.
           As a result, there is no output to stderr if NO_CONSOLE_IO is defined.
           Adaptive mapping to make bg uniform (adaptmap.c).  A few bug fixes.
           New PostScript output functions for embedding PS files
           (prog/converttops).  Generalized some image enhancement functions.
           New functions for generating hit-miss sels.

    1.29   12 Nov 05
           More flexible blending of two images, with and without colormaps
           (see blend.c).  Painting colormapped images through masks, etc
           (see paintcmap.c).  More flexible interface for gamma and
           contrast enhancement (see enhance.c).

    1.28   8 Oct 05
           Removed all pix colormaps for 1 bpp.  Allow programmatic resetting
           of binary morphology boundary conditions.  Added (yet) another
           simple octcube color quantizer.  New colormap operations.

    1.27   24 Sep 05
           Renamed many of the enums and typedefs to avoid namespace
           collisions.  This includes structs and typedefs for BMP.
           Interface change to pixClipRectangle(); apologies to everyone
           whose code is broken by these changes -- I hope it's worth it.
           Removed colormap.h; simplified all colormap usage, hiding details
           from all but a few colormap functions.  Am now saving file format
           in the pix when an image is read, and can by default write
           out in this format.  Resolution info added for jpeg and png.
           Added L_INFO* macros and l_info* fctns for printing
           (e.g., debugging) info.  Suggestions and code kindly
           supplied by Dave Bryan, who helped solve compatibility issues
           with MINGW32 (e.g., in timing and directory functions).
           Added some blending and linear TRC functions.
           Generalized pixEqual() to include all cases with and without
           colormaps.  New regression tests in prog: ioformats, equaltest.

    1.26   24 Jul 05
           Generalized affine pointwise to do interpolation as well as
           sampling.  For both projective and bilinear transforms,
           implemented using both sampling and interpolation.
           Added function to remove keystoning by computing the necessary
           projective transform and doing it.  Also find baselines in text images.
           Added downscaling using accurate area-mapping over subpixels.

    1.25   25 Jun 05
           Better endian conversion fctns for 2 and 4 byte words.
           Remove colormaps before converting by thresholds.
           Added functions to read header parameters for png and tiff.

    1.24   5 Jun 05
           Added image splitting to allow printing in tiles (as several pages).
           Added new octree quantization function to generate 4 and 8 bpp
           colormapped output (not dithered).  Fixed bmp resolution.
           Added new flag for colormap removal (using dest depth based on
           src colormap).  Added I/O tests (prog/ioformats.c)

    1.23   10 Apr 05
           Added thresholding from 8 bpp to 2 and 4 bpp, allowing specification
           of both the number of output levels and whether or not a colormap
           is made.

    1.22   27 Mar 05
           Add pointer queue facility.  To demonstrate it, you can now
           generate a binary maze using a cellular automaton and find
           the shortest path between two points in the maze.  Add heap
           of pointers (keyed on the first field), which is used to
           implement a priority queue.  This is applied to search for
           a "least cost" path on a grayscale image (a generalization
           of a binary maze).

    1.21   28 Feb 05
           Read/write of colormaps to file.  For gplot, add a new
           latex output terminal.  Bring ptrs into 21st century by
           including stdint.h, and using uintptr_t for the ptr address
           arithmetic in arrayaccess.*.  This seems to be OK back to
           RH 7.0, but if you run into trouble with an earlier
           C compiler, let me know.  Also, use enums for global
           constants whenever possible, and qualify named constants
           (e.g., ADD --> ARITH_ADD, HORIZ --> MORPH_HORIZ) to avoid
           possible interactions with other libraries.

    1.20   31 Jan 05
           Speed up of tiffio and pngio with byte swap generating new pix.
           In textops.c, ability to split string into paragraphs,
           in preparation for more general typesetting.
           Automatic hit-miss Sel generation for pattern matching.
           Fast downscaling using a lowpass filter and subsampling.
           Generalization of several grayscale and color operations
           to work on colormapped images.  Improved scale-to-gray and
           scaling reduction operations to be antialiased for best results.

    1.19   30 Nov 04
           Additions to fileIO: (1) new jpeg reading options, such as
           returning warnings and scaled raster; (2) ability to write
           custom tiff flags.  Better tiling functions.
           Edge extraction, both with grayscale morphology
           and clipped convolution filters.  More general painting
           through a binary mask: pixSetMaskedGeneral().
           Unpacking from binary to 8, 16 and 32 bpp.  Thresholding
           and dithering from 8 bpp to 2 bpp ("dibitization").  New bitmap
           font facility, using a single rendered font in a variety of
           sizes: allows painting the text on an image (binary, gray, RGB).
           (People have asked for the ability to write text on images).

    1.18   25 Aug 04
           Changed typedefs of built-in types to avoid possible conflicts.
           Cleaned up and tested all programs in the prog directory.
           Simplified and fixed the pixSetMasked() and pixCombineMasked()
           functions.

    1.17   31 May 04
           Implemented distance function for 16 bpp.  We can now generate
           out 16 bpp PNG.  Simple programs for generating PS from a
           directory of g4tiff or jpeg images.  Changed implementation of
           erosion to allow either asymmetric or symmetric boundary conditions.
           The distinction is described on the binary morphology web page.
           Allow read/write of multipage TIFF files.  Implemented
           read/write of PNM files.

    1.16   31 Mar 04
           New depth conversion functions, improved conversion to false color,
           new contour rendering (onto 1 bpp or onto the src grayscale image),
           new orthogonal rotations, better interface for doing arithmetic
           on 2-d arrays using a pix, improved distance function.

    1.15   31 Jan 04
           Fast interpolated color rotation with 4x4 subpixels; has
           nearly the accuracy of the slower method using 16x16 subpixels.
           Demonstration of line removal from grayscale sketch in
           prog/lineremoval.c.  Conversion of grayscale to false color.
           Fixed shear and rotation functions to handle angle = 0.0 properly.
           Other small fixes and interface improvements.

    1.14   30 Nov 03
           Small implementation changes to list.c.  Better sorting
           routines for number arrays (numa), plus sorting for box
           arrays (boxa) and pix arrays (pixa).  PostScript wrapper
           for jpeg.  Better handling of colormaps, and a simple
           function to convert an RGB pix with not more than 256
           colors to the smallest colormapped pix.  PS output wrappers
           for JFIF JPEG and TIFF G4 files.  Comments compatible
           with doxygen for automatic documentation.

    1.13   31 Oct 03
           Cleaned up documentation in src.  Made libraries and test programs
           ANSI C++ compliant.  Added special cases to rasterops for
           alignment to word boundaries.  Fixed pngio.c to work with
           most recent libpng (1.2.5).

    1.12   30 Jun 03
           Implemented border chain representation from a binary image,
           writes/reads a compressed version, and renders the original
           image back from the borders.   Also writes outline file out
           in svg format.  Number arrays (numa) and point arrays (pta)
           are also extended to 2nd level arrays (numaa, ptaa).
           Serialized I/O for boxa, pta, and pixa.

    1.11   31 May 03
           Implemented generic list handling, for doubly-linked
           list cons cells and arbitrary objects.

    1.10   14 Apr 03
           Implemented simple image enhancements in gray and color:
           gamma correction, contrast enhancement, unsharp masking.
           Extended smoothing via block convolution to color.
           Implemented auto-gen'd DWA version of hit-miss transform;
           the code for generating these hmt routines is very similar to
           that for DWA auto-gen'd erosion and dilation.

    1.9    28 Feb 03
           Implemented a safe, expandable byte queue.  As an example of
           its use, implemented memory-to-memory compression and decompression
           using zlib.  Generalized PS write to include RGB color.
           Implemented a method to find image skew.

    1.8    31 Jan 03
           Implemented a simple 1-pass color quantization with dithering,
           and improved the 2-pass octree color quantization.
           Documented with an application page, that includes jbig2.
           Added new general sampling operations and made a table
           that summarizes the available scaling operations.

    1.7    31 Dec 02
           Added pixHtmlViewer(), a formatter that allows portable viewing of
           a set of images (like a slide show) in a browser.
           Implemented better octree color quantization, with variable
           number of colors, pruning the octree for good color clusters,
           and fast traversal for pixel assignment to colormap.

    1.6    30 Nov 02
           Generalized shear and shear rotation to arbitrary locations
           about which the operation is performed.  Implemented in-place
           translation using pixRasteropIP().  Implemented arbitrary
           affine transform of image two ways: pointwise and sequential.
           Added binarization by error diffusion.  Added simple color
           quantization by octree.

    1.5    31 Oct 02
           Put jpeglib.h in local directory.  This, along with the jmorecfg.h
           file there prevents compiler warnings about redefined typedefs.
           Compiled everything with g++ to make strictly ansi C compatible.
           Added interface gplotFromFile() for simple file-based plotting with
           gnuplot 3.7.2.   Added functions to convert 2, 4 and 8 bpp
           color-mapped (i.e., palletted) images to 24 bpp color or
           8 bpp grayscale.  Added several jbig2 application cores that
           only require a simple wrapper to make into programs.

    1.4    30 Sep 02
           Added interface to gnuplot 3.7.2 and to x11 display of images.
           Added new functions with arrays of images for use in applications
           such as jbig2 encoders, along with a simple jbig2 implementation
           using either hausdorff or correlation scoring.  Added centroid
           finder for images.  For accessing image arrays from arrays of
           image arrays, added a "new reference" (NEW_REF) flag, with a
           ref count attached to the array.  Added power-of-2 binary
           expansion and reduction.

    1.3    30 Jun 02
           Extended connected components to 8.  Added morphological
           operations tophat and hdome, along with clipped arithmetic
           operators on grayscale images.  Fixed memory error in
           rasteropGeneralLow() that was found using valgrind.
           Tested most operations with valgrind for memory errors.
           Replaced integer arrays with number arrays, to include floats.
           Added arithmetic functions on grayscale images.

    1.2    30 May 02
           Added connected component utility, stack utility, pix arrays,
           line drawing and seed filling.  Binary reconstruction,
           both morphological and raster-oriented, are now supported
           for 4 and 8 connected fills.  Added the distance function
           on binary images, grayscale reconstruction, and grayscale
           morphology using the Gil-Werman method.

    1.1    30 Apr 02
           Added orthogonal rotations, binary scaling, PS output,
           binary reconstruction, integer arrays, structuring element
           input/output.

    1.0    25 Feb 02
           Initial distribution, with rasterops, binary morphology (two
           implementations: rasterops and dwa), affine transforms
           (translation, shear, scaling, rotation), fast convolution,
           and basic i/o (BMP, PNG and JPEG).