Hi mpl-users,
I have a web application in which I produce png files using
matplotlib. Unfortunately the files are quite big (up to ~300 kb). I
have however tried using the Linux tool pngnq to reduce the file size
with a factor ~3-4 with almost no degradation of the result. I
therefore wondered whether it is possible to setup matplotlib to do
something similar (from the source code the savefig method for png
files does not seem to use any keyword arguments). Here is the output
of the command pnginfo for the matplotlib output file and the pngnq
processed file:
0.0.0.0.0.0.20090517t00z.768.png...
Image Width: 768 Image Length: 328
Bitdepth (Bits/Sample): 8
Channels (Samples/Pixel): 4
Pixel depth (Pixel Depth): 32
Colour Type (Photometric Interpretation): RGB with alpha channel
Image filter: Single row per byte filter
Interlacing: No interlacing
Compression Scheme: Deflate method 8, 32k window
Resolution: 5039, 5039 (pixels per meter)
FillOrder: msb-to-lsb
Byte Order: Network (Big Endian)
Number of text strings: 0 of 0
Offsets: 0, 0
0.0.0.0.0.0.20090517t00z.768-nq8.png...
Image Width: 768 Image Length: 328
Bitdepth (Bits/Sample): 8
Channels (Samples/Pixel): 1
Pixel depth (Pixel Depth): 8
Colour Type (Photometric Interpretation): PALETTED COLOUR (256
colours, 0 transparent)
Image filter: Single row per byte filter
Interlacing: No interlacing
Compression Scheme: Deflate method 8, 32k window
Resolution: 0, 0 (unit unknown)
FillOrder: msb-to-lsb
Byte Order: Network (Big Endian)
Number of text strings: 0 of 0
Offsets: 0, 0
I am not using transparency for anything. For a web application a
reduction from 300 kb to 90 kb is really important so I hope you have
some good ideas. Otherwise I guess I will have to put in a call to
pngnq in my code (although I prefer to avoid calls to external
programs in the Python code when possible).
Best regards,
Jesper