On 07/22/2010 03:40 PM, j vickroy wrote: > Christopher Barker wrote: >> Jim Vickroy wrote: >> >>> The attachment is a simple script that creates a 2D array of unsigned, >>> 8-bit integers and uses matplotlib to save it as a PNG file. >>> >>> Unfortunately, the PNG file is much larger than expected -- apparently >>> because it is True-Color; on my MS Windows machine, bit depth, for the >>> file, is listed as 32 rather than the expected 8. >>> >> >> >>> Can matplotlib be used to accomplish this? If so, could someone direct >>> me to where this is discussed? >>> >> >> I don't think so directly. MPL uses a 32 bit image buffer internally, >> and that's what gets saved out in the PNG. >> >> 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
No need to use anything other than matplotlib for generating the figure--Chris's main point is that mpl does not provide configuration options for saving png files, but you can take such a png file, complete with image, colorbar, annotations, whatever, and use pil or ImageMagick (and there are probably several additional alternatives) to convert to a more compact png format. I took a quick look at the documentation of pil and IM, but unfortunately did not see any nice example of this--it is not obvious to me how to generate the palette. I suspect it is not hard, but it might take a while to figure it out from the docs. Programs like the following might do what you want: http://www.libpng.org/pub/png/apps/pngquant.html http://pngnq.sourceforge.net/ 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 ------------------------------------------------------------------------------ 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
