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 | .pnm |   |
✅ fully support | ✅ fully support | 150 lines of C |
| PNG | .png | |
❎ unsupported | ☑️ partially support | 240 lines of C |
| BMP | .bmp | |
☑️ partially support | ☑️ partially support | 180 lines of C |
| QOI | .qoi | |
✅ fully support | ✅ fully support | 240 lines of C |
| JPEG-LS | .jls | |
❎ unsupported | ☑️ partially support | 480 lines of C |
| JPEG-LS ext | .jlsx | |
☑️ support | ☑️ support | 760 lines of C |
| H.265 | .h265 | |
❎ unsupported | ☑️ partially support | 1730 lines of C |
Illustration of these image formats:
| format | Illustration |
|---|---|
| PNM | PNM (Portable Any Map), PGM (Portable Gray Map), and PPM (Portable Pix Map) are simple uncompressed image formats which store raw pixels. |
| PNG | PNG (Portable Network Graph) is the most popular lossless image compression format. |
| BMP | BMP (Bitmap Image File) is a popular uncompressed image formats which store raw pixels. |
| QOI | QOI (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 | JPEG-LS 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 . 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 to view .jls image online (but the website may not work sometimes). (2) Use UBC's JPEG-LS encoder/decoder . |
| JPEG-LS extension | This code is my implementation of JPEG-LS extension according to ITU-T T.870 specification for educational purpose. Note that the file header does NOT follow the specification! |
| H.265 | H.265/HEVC 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 or Elecard HEVC Analyzer . 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 . |
More illustration about this H.265 image encoder:
- 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)
If you installed MinGW, run following compiling command in CMD:
gcc src\*.c -O3 -o ImCvt.exewhich will get executable file ImCvt.exe
Also, you can use MSVC to compile. If you added MSVC (cl.exe) to your environment, run following compiling command in CMD:
cl src\*.c /Ox /FeImCvt.exewhich will get executable file ImCvt.exe
gcc src/*.c -O3 -o ImCvtwhich will get Linux binary file ImCvt
Run the program without any parameters to display usage:
> .\ImCvt.exe
|-----------------------------------------------------------------------|
| ImageConverter (v0.6) by https://github.com/WangXuan95/ |
|-----------------------------------------------------------------------|
| Usage: |
| ImCvt [-switches] <in1> -o <out1> [<in2> -o <out2>] ... |
| |
|-----------------------------------------------------------------------|
| Where <in> and <out> 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 |
| -<number> : 1. PNG RGB palette quantize color count |
| 2. JPEG-LS near value |
| 3. H.265 (qp-4)/6 value |
|-----------------------------------------------------------------------|
convert a PNM to a QOI:
ImCvt.exe image\P6.pnm -o image\P6.qoiconvert a QOI to a BMP:
ImCvt.exe image\P6.qoi -o image\P6.bmpconvert a BMP to a JPEG-LS, with near=1 (lossy):
ImCvt.exe image\P6.bmp -o image\P6.jls -1convert a BMP to a H.265 image file, with (qp-4)/6=2 (lossy):
ImCvt.exe image\P6.bmp -o image\P6.h265convert a BMP to a PNG:
ImCvt.exe image\P6.bmp -o image\P6.pngconvert a BMP to a PNG by quantize to 16-color palette:
ImCvt.exe image\P6.bmp -o image\P6_16.png -16convert 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
[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