6.9. Use sRGB Profile

6.9. Use sRGB Profile
	6. The “Image” Menu

When checked, Use sRGB Profile assigns a GIMP built-in sRGB color space to your image.

Also, if you've selected to display the image's assigned ICC color profile in the window title (which is the default) or status bar (see Image Title & Statusbar Format preferences), checking Use sRGB Profile will show “GIMP built-in sRGB” in the title or status bar in place of the image's assigned color profile.

	注意
	For images without color profile, or that have a sRGB profile Use sRGB Profile is disabled and checked by default. For images that have a different color profile this option will be enabled and unchecked. It's best to leave it that way unless you know what you are doing.

6.9.1. Activating the Command

You can access this command from the main menu through Image → Color Management → Use sRGB Profile.

6.9.2. Usage Notes regarding Use sRGB Profile

The best possible advice is to never check Use sRGB Profile when you are using a different color profile.

6.9.3. What does GIMP do when Use sRGB Profile is checked?

When you check the option to Use sRGB Profile, GIMP does two things:

Whatever ICC profile is currently assigned to the image, is stored (pending subsequent editing, Encoding, and Color Management actions), but isn't used. And then a built-in GIMP sRGB profile is assigned in place of the previously assigned ICC profile:
- If the image is in Non-linear encoding, the ICC profile "GIMP built-in sRGB" is assigned.
- If the image is in Linear light encoding, the ICC profile "GIMP built-in Linear sRGB" is assigned.
You can confirm that one of GIMP's built-in sRGB color spaces has been assigned by selecting Image → Image Properties and checking the Color Profile.

6.9.4. When Use sRGB Profile is checked, what happens to the image and the image appearance?

	注意
	Assigning a new profile to an image doesn't change the image's actual channel values. Assigning a new ICC profile only changes the meaning of these values, which means the image appearance will change (unless the original and new profile are functionally equivalent).

When Use sRGB Profile is checked, one of GIMP's built-in sRGB profiles is assigned to the image. Assigning a new ICC profile to an image doesn't change the image's channel values, but it does more or less drastically change the image's appearance:

If the image was already in one of GIMP's built-in color spaces (or if the assigned ICC profile is a profile that is functionally equivalent to the assigned GIMP built-in sRGB profile) then the image's appearance will not change.
If the image was not already in one of GIMP's built-in color spaces (and is not in a color space that is functionally equivalent to the assigned GIMP built-in sRGB profile), the image's appearance will change more or less drastically depending on three things:
- What GIMP channel encoding — Linear light or Non-linear — the image was in before the Use sRGB Profile box was checked.
- How far the image's originally assigned ICC profile's channel encoding ("TRC") is from the GIMP channel encoding.
- How far the image's originally assigned ICC profile's Red, Green, and Blue chromaticities are from GIMP's built-in sRGB chromaticities.

6.9.5. A screenshot showing an example of incorrect image appearance after checking Use sRGB Profile

The image is color managed: An ICC profile is assigned to the image, and that profile is being used to send the image colors to the screen. After checking Use sRGB Profile, one of GIMP's built-in sRGB profiles has been incorrectly assigned to the image, so the colors look wrong.

In the screenshot below, the channel encoding of the original profile matches the GIMP channel encoding (both are linear), but the “LargeRGB-elle-V4-g10.icc” profile chromaticities don't match the GIMP built-in sRGB chromaticities. So after checking Use sRGB Profile, the tonality is correct but the colors are wrong. The image is still color managed, but it's color managed using the wrong ICC profile:

图 16.60. A screenshot illustrating the effect of checking use sRGB.

Image using LargeRGB-elle-V4-g10.icc profile.

Same image after checking Use sRGB Profile.

	小心
If your image's originally assigned ICC profile doesn't have the same channel encoding and chromaticities as the GIMP built-in sRGB profile, and you check and then immediately change your mind and uncheck Use sRGB Profile, the originally assigned ICC profile will be reassigned to your image and your image channel values will be unchanged. Otherwise, whether or not you can recover the originally assigned ICC profile and correct colors for your image depends on what else you've done between the checking and unchecking of Use sRGB Profile. Again, the best possible advice is to never check Use sRGB Profile.

小心

If your image's originally assigned ICC profile doesn't have the same channel encoding and chromaticities as the GIMP built-in sRGB profile, and you check and then immediately change your mind and uncheck Use sRGB Profile, the originally assigned ICC profile will be reassigned to your image and your image channel values will be unchanged.

Otherwise, whether or not you can recover the originally assigned ICC profile and correct colors for your image depends on what else you've done between the checking and unchecking of Use sRGB Profile.

Again, the best possible advice is to never check Use sRGB Profile.