Leptonica Library
The library supports many operations that are useful on

* Document images
* Natural images

Fundamental image processing and image analysis operations

* Rasterop (aka bitblt)
* Affine transforms (scaling, translation, rotation, shear) on images of arbitrary pixel depth
* Binary and grayscale morphology, rank order filters, and convolution
* Seedfill and connected components
* Image transformations with changes in pixel depth, both at the same scale and with scale change
* Pixelwise masking, blending, enhancement, arithmetic ops, etc.

Ancillary utilities

* I/O for standard image formats (jpg, png, tiff, bmp, pnm, gif, ps)
* Utilities to handle arrays of image-related data types (e.g., pixa, boxa, pta)
* Utilities for stacks, generic arrays, queues, heaps, lists; number and string arrays; etc.

Examples of some applications enabled and implemented

* Octcube-based color quantization (w/ and w/out dithering)
* Modified median cut color quantization (w/ and w/out dithering)
* Skew determination of text images
* Segmentation of page images with mixed text and images
* jbig2 unsupervised classifier
* Border representations of 1 bit/pixel images and raster conversion for SVG
* Postscript wrapping (levels 1, 2) of images for device-independent output
* Connectivity-preserving thinning and thickening of 1 bit/pixel images
* Search for least-cost paths on binary and grayscale images
* Barcode reader for 1D barcodes (very early version as of 1.55)

Implementation characteristics

* Efficient: image data is packed binary (into 32-bit words); operations on 32-bit data whenever possible
* Simple: small number of data structures; simplest implementations provided that are efficient
* Thread-safe: no non-const global vars
* Consistent: data allocated on the heap with simple ownership rules; function names usually begin with primary data structure (e.g., pix)
* Robust: all ptr args checked; extensive use of accessors; exit not permitted
* Tested: thorough regression tests provided for most basic functions; valgrind tested
* Ansi C: automatically generated prototype header file
* Portable: endian-independent; builds in linux, osx, mingw, cygwin, windows
* Documentation: large number of in-line comments; web pages for further background
* Examples: many programs provided to test and show usage of approx. 1500 functions in the library

Open Source Projects that use Leptonica

* php (scripting language for dynamic web pages)
* tesseract (optical character recognition)
* jbig2enc (encodes multipage binary image documents with jbig2 compression)