Einar M. Einarsson wrote: > Hi all, > > I'm trying to find ways to make the file-size of my PNG images smaller. > > When I generate my 660*440px image I get a big 168kb file. > (8bit RGB color model, has an alpha channel (need that) but no > interlacing scheme) > > Here it is: > http://metphys.org/eme/T05.png > > I'm using the savefig method of-course. > > > To see how much I could compress it I used pngcrush (the best tool > according to the interwebs) and got it down to 128kb. > > But thats still way to large for my intended use. (plotting results > from an operational weather model, see. www.belgingur.is > We are currently using IDL.) > > From what I've read about PNG files, which is supposed to be rather > compact image format, it seems to me that the most effective way is > to have an indexed color table. > > So to cut it short: > > Is there any way to save a PNG file with an indexed color table?
Perhaps this should be supported natively in mpl; but until it is, you can do the conversion after the fact using pngquant or pngnq. Presumably, if you don't in fact have more than 256 colors, this conversion will be lossless. I have not tried this; my suggestion is based on the descriptions of pngquant and pngnq packages in Ubuntu feisty. Here is the latter: -------------------------------- tool for optimizing PNG (Portable Network Graphics) images Pngnq is a tool for quantizing 32-bit RGBA PNG images to 8-bit RGBA pallete PNG. It's is an adaptation by Stuart Coyle of Greg Roelf's pnqquant. While pngquant uses a median cut algorithm, Pngnq uses Anthony Dekker's neuquant algorithm (http://members.ozemail.com.au/~dekker/NEUQUANT.HTML), generally resulting in better looking results than pngquant. Optimizers (like pngcrush and optipng) optimize the compression, usually losslessly. pngnq quantizes colors down to 256 (or fewer) distinct RGBA combinations, which is quite lossy. Optimized PNGs are usually two to four times smaller than the 32-bit versions. Homepage: http://www.cybertherial.com/pngnq/pngnq.html ----------------------------------------------- > > Or do you see any other way to shrink the files? > > > Best regards. > Einar M. Einarsson > www.belgingur.is > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > Matplotlib-users mailing list > Matplotlib-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/matplotlib-users ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Matplotlib-users mailing list Matplotlib-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/matplotlib-users
