>> You can post-process the image with something like ImageMagick. >> >> Another alternative is to use PIL -- you can grab the matplotlib buffer, >> make a PIL image out of it, and use PIL to convert to an 8-bit palleted >> image. >> >> For that matter, you could probably bypass MPL, and use numpy to create >> the 8-bit image you want, and PIL to save it as a PNG. >> >> -Chris >> >> Thanks much for the helpful information. I will revisit PIL; I tried >> matplotlib because of other requirements (colorbar, various figure >> annotations) which did not appear to be readily available in PIL. At this >> stage, it depends on how important the requirement is to reduce the size of >> the PNG images. >> > -- jv
Try optipng: http://optipng.sourceforge.net/ Here I am running it on a gray-scale image created by mpl; it was generated in such a way that there are only 100 distinct shades of gray. You can see that it reduces the file size by quite a bit, converting it from RGBA to grayscale. This is lossless. For this to work, you have to make sure you have no more than 256 distinct colors--they don't have to be gray. -rw-rw-r-- 1 efiring efiring 8458 2010-07-22 16:26 grayfig.png efir...@manini:~$ optipng grayfig.png OptiPNG 0.6.3: Advanced PNG optimizer. Copyright (C) 2001-2009 Cosmin Truta. ** Processing: grayfig.png 800x600 pixels, 4x8 bits/pixel, RGB+alpha Reducing image to 8 bits/pixel, grayscale Input IDAT size = 8352 bytes Input file size = 8458 bytes Trying: zc = 9 zm = 8 zs = 0 f = 0 IDAT size = 3721 zc = 9 zm = 8 zs = 0 f = 5 IDAT size = 3301 zc = 9 zm = 8 zs = 1 f = 5 IDAT size = 3286 Selecting parameters: zc = 9 zm = 8 zs = 1 f = 5 IDAT size = 3286 Output IDAT size = 3286 bytes (5066 bytes decrease) Output file size = 3377 bytes (5081 bytes = 60.07% decrease) efir...@manini:~$ ll grayfig.png -rw-rw-r-- 1 efiring efiring 3377 2010-07-22 16:26 grayfig.png Eric ------------------------------------------------------------------------------ This SF.net email is sponsored by Sprint What will you do first with EVO, the first 4G phone? Visit sprint.com/first -- http://p.sf.net/sfu/sprint-com-first _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
