# ImCvt **Repository Path**: wangxuan95/ImCvt ## Basic Information - **Project Name**: ImCvt - **Description**: A lightweight image converter which supports PNG, PNM, BMP, QOI, JPEG-LS, and H.265 intra-frame. - **Primary Language**: C - **License**: MIT - **Default Branch**: main - **Homepage**: https://github.com/WangXuan95/ImCvt - **GVP Project**: No ## Statistics - **Stars**: 0 - **Forks**: 1 - **Created**: 2025-04-26 - **Last Updated**: 2025-08-01 ## Categories & Tags **Categories**: Uncategorized **Tags**: image-compression, BMP, qoi, jpeg-ls, h265 ## README ![language](https://img.shields.io/badge/language-C-green.svg) ![build](https://img.shields.io/badge/build-Windows-blue.svg) ![build](https://img.shields.io/badge/build-linux-FF1010.svg) ImCvt =========================== **ImCvt** is a **image format converter** which supports several image formats. **ImCvt** is written in C (C99), contains the simplest, standalone implementation of the encoders/decoders of some image formats, the purpose is to help one understand these image compression formats and algorithms swiftly. **ImCvt** supports: | format | suffix | supported color | convert from (decode) | convert to (encode) | source code | | :----------------------------------------------------------: | :----: | :----------------------------------------------------------: | :---------------------------------------- | :---------------------------------------- | :-------------------------------------: | | **[PNM](https://netpbm.sourceforge.net/doc/pnm.html)** | .pnm | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) ![rgb24](https://img.shields.io/badge/-RGB24-c534e0.svg) | :white_check_mark: fully support | :white_check_mark: fully support | [150 lines of C](./src/imageio_pnm.c) | | **[PNG](https://en.wikipedia.org/wiki/PNG)** | .png | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) ![rgb24](https://img.shields.io/badge/-RGB24-c534e0.svg) | :negative_squared_cross_mark: unsupported | :ballot_box_with_check: partially support | [240 lines of C](./src/imageio_png.c) | | **[BMP](https://en.wikipedia.org/wiki/BMP_file_format)** | .bmp | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) ![rgb24](https://img.shields.io/badge/-RGB24-c534e0.svg) | :ballot_box_with_check: partially support | :ballot_box_with_check: partially support | [180 lines of C](./src/imageio_bmp.c) | | **[QOI](https://qoiformat.org/)** | .qoi | ![rgb24](https://img.shields.io/badge/-RGB24-c534e0.svg) | :white_check_mark: fully support | :white_check_mark: fully support | [240 lines of C](./src/imageio_qoi.c) | | **[JPEG-LS](https://www.itu.int/rec/T-REC-T.87/en)** | .jls | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) ![rgb24](https://img.shields.io/badge/-RGB24-c534e0.svg) | :negative_squared_cross_mark: unsupported | :ballot_box_with_check: partially support | [480 lines of C](./src/imageio_jls.c) | | **[JPEG-LS ext](https://www.itu.int/rec/T-REC-T.870/en)** | .jlsx | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) | :ballot_box_with_check: support | :ballot_box_with_check: support | [760 lines of C](./src/imageio_jlsx.c) | | **[H.265](https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding)** | .h265 | ![gray8](https://img.shields.io/badge/-Gray8-lightgray.svg) | :negative_squared_cross_mark: unsupported | :ballot_box_with_check: partially support | [1730 lines of C](./src/imageio_hevc.c) | Illustration of these image formats: | format | Illustration | | :----------------------------------------------------------: | :----------------------------------------------------------- | | **[PNM](https://netpbm.sourceforge.net/doc/pnm.html)** | **[PNM](https://netpbm.sourceforge.net/doc/pnm.html)** (Portable Any Map), **[PGM](https://netpbm.sourceforge.net/doc/pgm.html)** (Portable Gray Map), and **[PPM](https://netpbm.sourceforge.net/doc/ppm.html)** (Portable Pix Map) are simple uncompressed image formats which store raw pixels. | | **[PNG](https://en.wikipedia.org/wiki/PNG)** | **[PNG](https://en.wikipedia.org/wiki/PNG)** (Portable Network Graph) is the most popular lossless image compression format. | | **[BMP](https://en.wikipedia.org/wiki/BMP_file_format)** | **[BMP](https://en.wikipedia.org/wiki/BMP_file_format)** (Bitmap Image File) is a popular uncompressed image formats which store raw pixels. | | **[QOI](https://qoiformat.org/)** | **[QOI](https://qoiformat.org/)** (Quite OK Image) is a simple, fast lossless RGB image compression format. This project implements a simple QOI encoder/decoder in only 240 lines of C. | | **[JPEG-LS](https://www.itu.int/rec/T-REC-T.87/en)** | **[JPEG-LS](https://www.itu.int/rec/T-REC-T.87/en)** is a lossless/lossy image compression standard which can get better grayscale compression ratio compared to PNG and Lossless-WEBP. 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 specification of JPEG-LS is [ITU-T T.87](https://www.itu.int/rec/T-REC-T.87/en) . **ImCvt** implements a simple JPEG-LS encoder in only 480 lines of C. However, **ImCvt** do not support JPEG-LS decoder yet. Here are two ways to decompress a .jls file: (1) Use [this website](https://products.groupdocs.app/viewer/JLS) to view .jls image online (but the website may not work sometimes). (2) Use [UBC's JPEG-LS encoder/decoder](./JPEG-LS_UBC_v2.2.zip) . | | **[JPEG-LS extension](https://www.itu.int/rec/T-REC-T.870/en)** | This code is my implementation of **JPEG-LS extension** according to [ITU-T T.870](https://www.itu.int/rec/T-REC-T.870/en) specification for educational purpose. Note that the file header does NOT follow the specification! | | **[H.265](https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding)** | **[H.265/HEVC](https://en.wikipedia.org/wiki/High_Efficiency_Video_Coding)** is a video coding standard. This project implements a lightweight grayscale 8-bit H.265/HEVC intra-frame image compressor in only 1730 lines of C for educational purpose. Note that this code only offers H.265/HEVC compressor instead of decompressor. To decompress and view the compressed .h265 image file, you can use [File Viewer Plus](https://fileinfo.com/software/windows_file_viewer) or [Elecard HEVC Analyzer](https://elecard-hevc-analyzer.software.informer.com/) . For more knowledge about H.265, see [H.265/HEVC 帧内编码详解：CU层次结构、预测、变换、量化、编码](https://zhuanlan.zhihu.com/p/607679114) . | More illustration about this [H.265 image encoder](./src/imageio_hevc.c): - Quality parameter can be 0~4, corresponds to Quantize Parameter (QP) = 4, 10, 16, 22, 28. - CTU : 32x32 - CU : 32x32, 16x16, 8x8 - TU : 32x32, 16x16, 8x8, 4x4 - The maximum depth of CU splitting into TUs is 1 (each CU is treated as a TU, or divided into 4 small TUs, while the small TUs are not divided into smaller TUs). - part_mode: The 8x8 CU is treated as a PU (`PART_2Nx2N`), or divided into 4 PUs (`PART_NxN`) - Supports all 35 prediction modes - Simplified RDOQ (Rate Distortion Optimized Quantize) 　 　 # Compile ### compile in Windows (MinGW) If you installed MinGW, run following compiling command in CMD: ```powershell gcc src\*.c -O3 -o ImCvt.exe ``` which will get executable file [**ImCvt.exe**](./ImCvt.exe) ### compile in Windows (MSVC) Also, you can use MSVC to compile. If you added MSVC (cl.exe) to your environment, run following compiling command in CMD: ```powershell cl src\*.c /Ox /FeImCvt.exe ``` which will get executable file [**ImCvt.exe**](./ImCvt.exe) ### compile in Linux (gcc) ```bash gcc src/*.c -O3 -o ImCvt ``` which will get Linux binary file **ImCvt** 　 　 # Usage Run the program without any parameters to display usage: ``` > .\ImCvt.exe |-----------------------------------------------------------------------| | ImageConverter (v0.6) by https://github.com/WangXuan95/ | |-----------------------------------------------------------------------| | Usage: | | ImCvt [-switches] -o [ -o ] ... | | | |-----------------------------------------------------------------------| | Where and can be: | |--------|---------------------------------|-------|--------|-----|-----| | | | gray | RGB | | | | suffix | format name | 8-bit | 24-bit | in | out | |--------|---------------------------------|-------|--------|-----|-----| | .bmp | Bitmap Image File (BMP) | yes | yes | yes | yes | | .pnm | Portable Any Map (PNM) | yes | yes | yes | yes | | .pgm | Portable Gray Map (PGM) | yes | no | yes | yes | | .ppm | Portable Pix Map (PPM) | no | yes | yes | yes | | .qoi | Quite OK Image (QOI) | no | yes | yes | yes | | .png | Portable Network Graphics (PNG) | yes | yes | no | yes | | .jls | JPEG-LS Image (JLS) | yes | yes | no | yes | | .jlsx | JPEG-LS extension (ITU-T T.870) | yes | no | yes | yes | | .h265 | H.265/HEVC Image | yes | no | no | yes | |--------|---------------------------------|-------|--------|-----|-----| | | | switches: -f : force overwrite of output file | | - : 1. PNG RGB palette quantize color count | | 2. JPEG-LS near value | | 3. H.265 (qp-4)/6 value | |-----------------------------------------------------------------------| ``` ### Example Usage convert a PNM to a QOI: ```powershell ImCvt.exe image\P6.pnm -o image\P6.qoi ``` convert a QOI to a BMP: ```powershell ImCvt.exe image\P6.qoi -o image\P6.bmp ``` convert a BMP to a JPEG-LS, with near=1 (lossy): ```powershell ImCvt.exe image\P6.bmp -o image\P6.jls -1 ``` convert a BMP to a H.265 image file, with (qp-4)/6=2 (lossy): ```powershell ImCvt.exe image\P6.bmp -o image\P6.h265 ``` convert a BMP to a PNG: ```powershell ImCvt.exe image\P6.bmp -o image\P6.png ``` convert a BMP to a PNG by quantize to 16-color palette: ```powershell ImCvt.exe image\P6.bmp -o image\P6_16.png -16 ``` convert a grayscale PNM to JPEG-LS extension with near=1 (lossy), and then convert it back to BMP: ``` ImCvt.exe image\P5.pnm -o image\P5.jlsx -1 ImCvt.exe image\P5.jlsx -o image\P5.bmp ``` 　 　 # Related links [1] Official website of QOI : https://qoiformat.org/ [2] ITU-T T.87 : JPEG-LS baseline specification : https://www.itu.int/rec/T-REC-T.87/en [3] UBC's JPEG-LS baseline Public Domain Code : http://www.stat.columbia.edu/~jakulin/jpeg-ls/mirror.htm [4] pillow-jpls library for Python : https://pypi.org/project/pillow-jpls [5] PNM Image File Specification : https://netpbm.sourceforge.net/doc/pnm.html [6] uPNG: a simple PNG decoder: https://github.com/elanthis/upng [7] FPGA-based Verilog QOI compressor/decompressor: https://github.com/WangXuan95/FPGA-QOI [8] FPGA-based Verilog JPEG-LS encoder (basic version which support 8-bit gray lossless and lossy compression) : https://github.com/WangXuan95/FPGA-JPEG-LS-encoder [9] FPGA-based Verilog JPEG-LS encoder (ultra high performance version which support 8-bit gray lossless compression) : https://github.com/WangXuan95/UH-JLS [10] H.265/HEVC 帧内编码详解：CU层次结构、预测、变换、量化、编码：https://zhuanlan.zhihu.com/p/607679114 [11] The H.265/HEVC reference software HM: https://github.com/listenlink/HM [12] NBLI: a fast, better lossless image format: https://github.com/WangXuan95/NBLI [13] ITU-T T.870 : JPEG-LS extention specification : https://www.itu.int/rec/T-REC-T.870/en [14] A comparison of many lossless image compression formats: https://github.com/WangXuan95/Image-Compression-Benchmark