Version Notes for Leptonica


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

1.68 – 14 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.c.

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:

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 “Document Image Applications” in Mathematical Morphology: theory and applications (see: Document Image Analysis) (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.c 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 situations.

  • New functions for initialization and random insertion with pixcomp.c.

  • 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:

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 to 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

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 psio1.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 prototype 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:

1.61 – 26 Apr 09

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}.

  • Improved connected component filtering, with logical functions applied to indicator arrays (pix4.c, pixafunc1.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:

  • 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.

Earlier Versions

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
       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,
       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,
       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
       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

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
       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, 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()

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

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).