ICC Profiles #4
Description
Different monitors and printers will generate slightly different colors. The International Color Consortium (ICC) defined a color profile system. ICC Profiles adjust the rendered colors to minimize any variations. When used properly, colors will look as close as possible regardless of the display. An ICC Profile may be embedded in the image file as metadata, applied by an application, and/or associated with a monitor.
The two common versions of the ICC Profile format are version 2 and version 4. Version 2 uses tone reproduction curves to transform the color space. Version 4 uses complex matrix transforms with look-up tables. A single ICC Profile may contain multiple definitions. If version 4 is available, then it will be used. Otherwise, it will fall-back to version 2.
Some browsers fully support ICC Profiles and adjust pictures that are displayed. Other browsers support ICC version 2 but not version 4, and many browsers do not support any color profiles.
Beyond ICC Profiles are a few other color management options. The PNG file format is the most common. PNG files may include definitions for gamma corrections, white point select, and chromasticity (the three main components for any color normalization system). However, not every application supports PNG color corrections, support may be partial, and there can be a prioritization conflict if the file contains both PNG color correction and ICC Profile information.
Color profiles are created and applied by applications. They explicitly denote a post-file color alteration. FotoForensics intentionally renders images without applying the color profile in order to prevent additional alterations that could be distorted by the profile. Regardless of your web browser, FotoForensics' algorithms will always evaluate the image without applying the color profile.
Microsoft's color profile support is inconsistent between applications. This means that some images may look different when viewed under Internet Explorer, Microsoft Photo Viewer, or other Microsoft applications.
- Chrome: supports JPEG images with embedded ICC Profiles. It only supports ICC Profile version 2. If a JPEG has an embedded color profile with version 2 information, then it will be applied to the image
- Firefox ?-39 support JPEG images with embedded ICC Profiles version 2. If a JPEG has an embedded color profile with version 2 information, then it will be applied to the image
- Firefox 40+: the desktop browser defaults to no color management support. Pictures will appear with no color profile applied
- Internet Explorer fully supports JPEG images with embedded ICC Profile information. It supports the ICC Profile version 4 standard. If a picture has an embedded color profile, then it will be applied to the image.
Microsoft also developed their own proprietary ICC Profile extension. Beginning with Windows Vista, images containing the Windows Color System (WCS) definition may have it applied to the picture - Safari: uses Apple's color management system. This system does not fully implement the ICC Profile versions 2 or 4 standards. Because of this problem, pictures displayed by Safari may look different when compared to other platforms.
Technically, ICC Profiles may include data from the version 2 specification (ICCv2), version 4 (ICCv4), or both. Apple's CMS correctly displays pictures that only use ICCv4. Pictures that use only ICCv2 are almost displayed correctly, but the colors may be a little off. However, if the picture's profile includes both ICCv2 and ICCv4 information, then Apple will apply the ICCv2 information instead of the ICCv4 information. This contradicts the ICC standard, which says to apply ICCv4 when it is present. - Mobile Chrome: does not apply any embedded ICC color profiles. Depending on the version, may apply embedded PNG gamma corrections
- Mobile Firefox: does not apply any embedded ICC color profiles
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