Function isGrayICCProfile

depends/lodepng/lodepng.cpp:5793–5805

}

static unsigned isGrayICCProfile(const unsigned char* profile, unsigned size) {
  /*
  It is a gray profile if bytes 16-19 are "GRAY", rgb profile if bytes 16-19
  are "RGB ". We do not perform any full parsing of the ICC profile here, other
  than check those 4 bytes to grayscale profile. Other than that, validity of
  the profile is not checked. This is needed only because the PNG specification
  requires using a non-gray color model if there is an ICC profile with "RGB "
  (sadly limiting compression opportunities if the input data is grayscale RGB
  data), and requires using a gray color model if it is "GRAY".
  */
  if(size < 20) return 0;
  return profile[16] == 'G' &&  profile[17] == 'R' &&  profile[18] == 'A' &&  profile[19] == 'Y';
}

static unsigned isRGBICCProfile(const unsigned char* profile, unsigned size) {
  /* See comment in isGrayICCProfile*/