All images below have the same RGB values, but the sRGB and Gamma information in the PNGs is different. Depending on your browser and operating-system color profile, all images may look the same or different.
| CSS | GIF | PNG bare | PNG sRGB perceptual | PNG sRGB rel. Col'ic | PNG sRGB Saturation | PNG sRGB abs. col'ic | PNG sRGB perc., g=2.2 | PNG g=2.2 | PNG g=1.8 |
|---|---|---|---|---|---|---|---|---|---|
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#111
#444
#888
#ccc
#fff
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#051105
#134113
#268026
#3abf3a
#4dff4d
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Of the mainstream browsers, only Apple Safari is supposed to use embedded color profiles, which means that it transforms the RGB values before sending them to the operating system (Mac OS X). The operating system then applies the system color profile (generic sRGB or a monitor-specific profile) before sending the data to the monitor.
The other mainstream browsers (Firefox 1.5/2.0, Opera 8/9, Internet Explorer 6/7) presumably pass the raw RGB values from the images without any transformation to the operating system, which would mean that all images look identical.
If you wish, you can see the LCD test images in a version without color profiles.
Explanation of the image captions:
- CSS
- Raw RGB values in the web page stylesheet. Supposedly sRGB, but the mainstream browsers treat them as raw RGB values.
- GIF
- GIF files do not contain color profile information. It should be displayed as raw RGB, like the CSS column.
- PNG bare
- PNG format, with all color profile information removed. Should look the same as CSS and GIF.
- PNG sRGB, perceptual
- PNG tagged as perceptual sRGB, which is one of the four ways a PNG can be tagged. See PNG: The definite guide for details. One would expect this to look just like bare PNG when displayed through an sRGB profile.
- PNG sRGB, relative colorimetric
- Another sRGB tag.
- PNG sRGB, saturation-preserving
- Another sRGB tag.
- PNG sRGB, absolute colorimetric
- Another sRGB tag.
- PNG sRGB, perceptual with gamma 2.2
- sRGB-tagged, but with gamma 2.2 (or rather, 1/2.2 = 0.45455) as a fall-back.
- PNG g=2.2
- PNG format, embedded gamma 2.2. This should be similar to sRGB format.
- PNG g=1.8
- PNG format, embedded gamma 1.8, which is what was traditionally used on Apple Macintosh systems.
See also: The Sad Story of PNG Gamma "Correction" .
