savepng is a very efficient PNG image compression MEX-routine that outperforms MATLAB's built-in imwrite in compression times and produced file sizes. For a typical figure size at the default compression level, savepng is ~5.8 times faster, with a file size identical to imwrite. At the highest compression level, savepng can take more time than imwrite, but produce a file that is ~40% smaller.
Compression levels 0-2 are based on public-domain fpng
Compression levels 3-14 are based on MIT licensed libdeflate
savepng(CDATA,filename[,Compression[,Resolution]])Where,
CDATAis a standard MATLAB image m-by-n-by-3 or m-by-n-by-4 (when supplying alpha channel) matrix. This matrix can be obtained usinggetframecommand or, for a faster implementation use undocumented hardcopy commandfilenamefile name of the image to write. Don't forget to add .png to the file name.CompressionOptional input argument. This argument takes on a number between 0 and 10 controlling the amount of compression. 0 implies no compresson, fastest option (though with more I/O this is not neccessarily the fastest option). 10 implies the highest level of compression, slowest option. Default value is 4.ResolutionOptional input argument. This argument specifies the resolution of the file being saved. Resolution is expressed in Dots-Per-Inch (DPI). Default resolution is 96 DPI.
| Compression | IMWRITE | OLD SAVEPNG | SAVEPNG | Improvement |
|---|---|---|---|---|
| 1 | 0.040558 | 0.011868 | 0.005611 | 7.3 |
| 2 | 0.040394 | 0.011964 | 0.006555 | 6.2 |
| 3 | 0.040248 | 0.014300 | 0.007754 | 5.3 |
| 4 | 0.040182 | 0.013509 | 0.009586 | 4.2 |
| 5 | 0.040481 | 0.014809 | 0.010105 | 4.0 |
| 6 | 0.040486 | 0.018222 | 0.009939 | 4.1 |
| 7 | 0.040066 | 0.021582 | 0.010500 | 3.8 |
| 8 | 0.039954 | 0.027397 | 0.010973 | 3.6 |
| 9 | 0.039727 | 0.032898 | 0.011946 | 3.3 |
| 10 | 0.040032 | 0.046404 | 0.016177 | 2.5 |
| 11 | 0.039856 | N/A | 0.019164 | 2.1 |
| Compression | IMWRITE | OLD SAVEPNG | SAVEPNG | Improvement |
|---|---|---|---|---|
| 1 | 196774.30 | 151091.37 | 323900.30 | 164.20% |
| 2 | 196774.30 | 136489.40 | 279062.47 | 141.81% |
| 3 | 196774.30 | 120649.57 | 141057.57 | 72.91% |
| 4 | 196774.30 | 124359.17 | 126171.43 | 65.32% |
| 5 | 196774.30 | 120649.57 | 124357.17 | 64.46% |
| 6 | 196774.30 | 117487.83 | 123128.23 | 63.81% |
| 7 | 196774.30 | 116918.57 | 118990.70 | 61.66% |
| 8 | 196774.30 | 116715.43 | 117603.43 | 60.95% |
| 9 | 196774.30 | 116388.90 | 116300.00 | 60.26% |
| 10 | 196774.30 | 115713.00 | 115652.83 | 59.82% |
| 11 | 196774.30 | N/A | 115602.50 | 59.79% |