PNG_FORMAT_RGB_COLORMAP

Undocumented in source but is binding to C. You might be able to learn more by searching the web for its name.
version(!PNG_VERSION_INFO_ONLY)
extern (C)
static if(PNG_SIMPLIFIED_READ_SUPPORTED || PNG_SIMPLIFIED_WRITE_SUPPORTED)
enum PNG_FORMAT_RGB_COLORMAP = (PNG_FORMAT_RGB | PNG_FORMAT_FLAG_COLORMAP);

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