C语言实现的 JPEG-LS 图像编码器。.zip

   # JPEG-LS encoder A simple JPEG-LS baseline (ITU-T T.87) image compressor (encoder) in C language. 　 # Background of JPEG-LS **JPEG-LS** (**JLS**) is a lossless/lossy image compression standard which has the best lossless compression ratio compared to PNG, Lossless-JPEG2000, Lossless-WEBP, Lossless-HEIF, etc. The standard specification of JPEG-LS is ITU-T T.87 [1], see https://www.itu.int/rec/T-REC-T.87/en **JPEG-LS** uses the maximum difference between the pixels before and after compression (**NEAR** value) to control distortion, **NEAR=0** is the lossless mode; **NEAR>0** is the lossy mode, the larger the **NEAR**, the greater the distortion and the greater the compression ratio. The file suffix name for **JPEG-LS** compressed image is .**jls** . 　 # Development progress - [x] gray 8 bit image lossless encode (near=0) - [x] gray 8 bit image lossy encode (near-lossless, near≥1) - [x] gray 9-16 bit image lossless encode (near=0) - [ ] gray 9-16 bit image lossy encode (near-lossless, near≥1) - [x] RGB 24 bit image lossless encode (near=0) - [x] RGB 24 bit image lossy encode (near-lossless, near≥1) - [x] RGB 48 bit image lossless encode (near=0) - [ ] RGB 24 bit image lossy encode (near-lossless, near≥1) 　 # Code list The code is in pure-C. See [src](./src) folder: - `JLS.c` : Implement a JLS encoder - `JLS.h` : Expose the JLS encoder function to users - `JLSMain.c` : A main program with `main()` function, which call the JLS encoder to achieve image file compression. 　 # Compile ### Compile in Windows (CMD) If you installed MinGW Compiler for Windows, you can compile using the command line (CMD). ```powershell gcc src/*.c -o JLSencode.exe -O3 -Wall ``` We'll get the executable file `JLSencoder.exe` . Here I've compiled it for you, see `JLSencoder.exe` . ### Compile in Linux Run the command in the current directory: ```bash gcc src/*.c -o JLSencode -O3 -Wall ``` We'll get the binary file `JLSencoder` . 　 # Run image compression This program can compress the following three types of image file to `.jls` compressed file. - PGM grayscale image file, whose specification is in https://netpbm.sourceforge.net/doc/pgm.html - PPM RGB image file, whose specification is in https://netpbm.sourceforge.net/doc/ppm.html - PNM grayscale or RGB image file, whose specification is in https://netpbm.sourceforge.net/doc/pnm.html There are some PGM and PPM files in [testimage ](./testimage)directory. ### Run image compress in Windows (CMD) Use the following command to compress a image file to a `.jls` file. ```bash .\JLSencode.exe <input-image-file> <output-file(.jls)> [near] ``` Where `[near]` is a optional parameter of range 0\~9 : - 0 : lossless (default) - 1\~9 : lossy. The larger the near value, the higher distortion and the lower compressed size. For example, the following command to compress `rgb1.ppm` in `testimage` folder to `rgb1.jls` with near=1 ```bash .\JLSencode.exe testimage\rgb1.ppm rgb1.jls 1 ``` ### Run image compress in Linux Use the following command to compress a image file to a `.jls` file. ``` ./JLSencode <input-image-file> <output-file(.jls)> [near] ``` 　 # Appendix: How to decompress .jls file? This repo do not have a JPEG-LS decompressor. There are several ways to decompress a .jls file: - The most convenient method: Try [this website](https://products.groupdocs.app/viewer/JLS) to view .jls image online (it may not work). - Use other JPEG-LS code or libraries such as UBC's JPEG-LS code [3] or CharLS [4]. - Use python `pillow` library and `pillow_jpls` library, see [5]. 　 # Reference [1] ITU-T T.87 : JPEG-LS baseline specification : https://www.itu.int/rec/T-REC-T.87/en [2] PNM Image File Specification : https://netpbm.sourceforge.net/doc/pnm.html [3] UBC's JPEG-LS baseline Public Domain Code : http://www.stat.columbia.edu/~jakulin/jpeg-ls/mirror.htm [4] CharLS, a C++ JPEG-LS library implementation : https://github.com/team-charls/charls [5] pillow-jpls library for Python - PyPI : https://pypi.org/project/pillow-jpls [6] FPGA-based Verilog JPEG-LS encoder (basic version which support 8-bit gray lossless and lossy) : https://github.com/WangXuan95/FPGA-JPEG-LS-encoder [7] FPGA-based Verilog JPEG-LS encoder (ultra high performance version which support 8-bit gray lossless) : https://github.com/WangXuan95/UH-JLS