I'm trying to convert some small PNG images from 32-bit color mode to indexed color mode.
For color images, I ran the command
convert IMGS/FLAME.png INDEXED_IMGS/FLAME.png and it converted fine. For an image that had only grayscale colors, I ran that same command (with the filename changed obviously) but I got a warning:
convert: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG 'INDEXED_IMGS/SHADOW.png' @ warning/png.c/MagickPNGWarningHandler/1748.
file IMGS/*.pngand got
IMGS/FLAME.png: PNG image data, 16 x 16, 8-bit/color RGBA, non-interlaced IMGS/SHADOW.png: PNG image data, 8 x 8, 8-bit/color RGBA, non-interlaced
which is expected; both images are in 8-bit RGBA mode (since that's the mode I created them in Photoshop). However, when I run
file INDEXED_IMGS/*.png I get
INDEXED_IMGS/FLAME.png: PNG image data, 16 x 16, 4-bit colormap, non-interlaced INDEXED_IMGS/SHADOW.png: PNG image data, 8 x 8, 8-bit grayscale, non-interlaced
The 4-bit colormap part checks out, but the grayscale part does not.
So my question is: how can I convert a grayscale image to indexed mode? What really gets me is that it starts out in RGBA mode like the color image, but for some reason it converts automatically to grayscale mode. Is there a way to prevent it from doing that?
I should add that I have a bash script that looks like this:
#!/bin/bash for img in IMGS/*.png; do file=$(basename $img) convert $img INDEXED_IMGS/$file done
so I don't wanna manually distinguish between grayscale and colored images. If there's a way to do so automatically with some command that's fine though.
Here is info about my ImageMagick tool:
Version: ImageMagick 7.0.8-42 Q16 x86_64 2019-04-24 https://imagemagick.org Copyright: © 1999-2019 ImageMagick Studio LLC License: https://imagemagick.org/script/license.php Features: Cipher DPC HDRI Modules OpenMP Delegates (built-in): bzlib freetype heic jng jp2 jpeg lcms ltdl lzma openexr png tiff webp xml zlib