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Color RGB/HSV values are different in Image Editor compared to any other UI Color field #117023

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opened 2024-01-11 12:27:18 +01:00 by DH · 8 comments
DH commented 2024-01-11 12:27:18 +01:00
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System Information
Operating system: Windows-10-10.0.19045-SP0 64 Bits
Graphics card: AMD Radeon RX 7900 XT ATI Technologies Inc. 4.6.0 Core Profile Context 23.12.1.231124

Blender Version
Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: d0dd92834a08
Worked: (newest version of Blender that worked as expected)

Short description of error
In Image Editor with Sample Pipette I get for the Color other RGB/HSV Values (probably this are right ones) as if I copy this exact color to Object Color or Material Color field or to any other Python Add-on color field which uses FloatVectorProperty.
The Color is actually the same but the single values R G B, H S V are different from the Image Editor to the Color Field.

Color Management is set so sRGB, Standard, Exposure 0.0, Gamma 1.0, Look None

Steps to reproduce the issue
Load any Texture in the Image Editor, zoom to any pixel,
set this specific color with the Color Picker Window - Eyedropper for Object Color or Material Color,
sample color with Sample Pipette in Image Editor.
Compare with values in the Color window of UI. The values are different.

BTW: Would be nice if the Sample Pipette can copy the Color to Clipboard with an Shortcut maybe +Ctrl

**System Information** Operating system: Windows-10-10.0.19045-SP0 64 Bits Graphics card: AMD Radeon RX 7900 XT ATI Technologies Inc. 4.6.0 Core Profile Context 23.12.1.231124 **Blender Version** Broken: version: 4.0.1, branch: blender-v4.0-release, commit date: 2023-11-16 16:40, hash: `d0dd92834a08` Worked: (newest version of Blender that worked as expected) **Short description of error** In Image Editor with Sample Pipette I get for the Color other RGB/HSV Values (probably this are right ones) as if I copy this exact color to Object Color or Material Color field or to any other Python Add-on color field which uses FloatVectorProperty. The Color is actually the same but the single values R G B, H S V are different from the Image Editor to the Color Field. Color Management is set so sRGB, Standard, Exposure 0.0, Gamma 1.0, Look None **Steps to reproduce the issue** Load any Texture in the Image Editor, zoom to any pixel, set this specific color with the Color Picker Window - Eyedropper for Object Color or Material Color, sample color with Sample Pipette in Image Editor. Compare with values in the Color window of UI. The values are different. BTW: Would be nice if the Sample Pipette can copy the Color to Clipboard with an Shortcut maybe +Ctrl
Color RGB_HSV different.png
253 KiB
Color RGB_HSV different.png
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DH changed title from Color RGB/HVS values are different in Image Editor compared to any other UI Color field to Color RGB/HSV values are different in Image Editor compared to any other UI Color field 2024-01-11 12:27:43 +01:00
Germano Cavalcante commented 2024-01-11 15:27:06 +01:00
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Thank you for the report but the issue is unclear, as there is no "steps to reproduce the issue".
Without clear steps, it is difficult to determine the exact cause and provide a solution.

However, I can provide some general information that might be helpful.
The color picker in Blender for RGB values is in the scene linear color space (hence the value are in the 0.0 to 1.0 range).
Blender follows a scene-referred workflow, whereas applications like Photoshop use a display-referred workflow.

If you want to input colors in the sRGB color space with "gamma correction" applied, you can use the Hex input. This will ensure that the values are interpreted correctly in the sRGB color space.

For more information on this topic, I recommend consulting the Blender manual:

A guideline for making a good bug report can be found at https://wiki.blender.org/wiki/Process/Bug_Reports

Thank you for the report but the issue is unclear, as there is no "steps to reproduce the issue". Without clear steps, it is difficult to determine the exact cause and provide a solution. However, I can provide some general information that might be helpful. The color picker in Blender for RGB values is in the scene linear color space (hence the value are in the 0.0 to 1.0 range). Blender follows a scene-referred workflow, whereas applications like Photoshop use a display-referred workflow. If you want to input colors in the sRGB color space with "gamma correction" applied, you can use the Hex input. This will ensure that the values are interpreted correctly in the sRGB color space. For more information on this topic, I recommend consulting the Blender manual: - [Color Management](https://docs.blender.org/manual/en/dev/render/color_management.html) - [Color Picker](https://docs.blender.org/manual/en/dev/interface/controls/templates/color_picker.html) _A guideline for making a good bug report can be found at https://wiki.blender.org/wiki/Process/Bug_Reports_
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DH commented 2024-01-12 01:42:21 +01:00
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I didn't post any steps because its already explained in description. But I had added them + screenshot. Hope this makes it clear.

I didn't post any steps because its already explained in description. But I had added them + screenshot. Hope this makes it clear.
DH closed this issue 2024-01-12 01:42:24 +01:00
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Richard Antalik commented 2024-01-16 21:10:02 +01:00
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This seems to be, because image colorspace is sRGB, while object color is in linear space, so color conversion happens. If you set image colorspace to Linear, you get the same color in color picker. Can you check what is colorspace of the image you are using?

This seems to be, because image colorspace is sRGB, while object color is in linear space, so color conversion happens. If you set image colorspace to Linear, you get the same color in color picker. Can you check what is colorspace of the image you are using?
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DH commented 2024-01-19 12:14:02 +01:00
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The Image PNG file is in sRGB, ofc. With not any other ColorSpace of Image I get the same values. The values in the Object Color field are 0.0XX, that is pretty small.
If you slide all R G B Values you see a curve like an e-function. I dont think this is linear.

for the #2f342e:

In Photoshop   in ImageE Sample    in ObjectC Color Picker
R 47 of 256         0.18              0.028
G 52 of 256         0.20              0.034
B 46 of 256         0.18              0.027

So Photoshop value (transfered to float) and ImageE Sample is same value, also the position in the Color Square, hence the correct one.
Hence Color Picker Window shows correct Color, but wrong values!

The Image PNG file is in sRGB, ofc. With not any other ColorSpace of Image I get the same values. The values in the Object Color field are 0.0XX, that is pretty small. If you slide all R G B Values you see a curve like an e-function. I dont think this is linear. for the #2f342e: ``` In Photoshop in ImageE Sample in ObjectC Color Picker R 47 of 256 0.18 0.028 G 52 of 256 0.20 0.034 B 46 of 256 0.18 0.027 ``` So Photoshop value (transfered to float) and ImageE Sample is same value, also the position in the Color Square, hence the correct one. Hence Color Picker Window shows correct Color, but wrong values!
Richard Antalik commented 2024-01-30 21:18:55 +01:00
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@Dominique-Herrmann I am not sure if I understand your last comment. I am not sure, what ImageE is. Colors you perceive as same color have different values in various colorspaces. I guess, that you assume, that color you see in UI, is linearly distributed from 0 to 1(255). That is true in sRGB space, but in linear space there this is non linear distribution.
In any case, I have looked in the code - it converts the sampled pixel from image color space to scene linear color space. This works as expected, so will close the report.

@Dominique-Herrmann I am not sure if I understand your last comment. I am not sure, what ImageE is. Colors you perceive as same color have different values in various colorspaces. I guess, that you assume, that color you see in UI, is linearly distributed from 0 to 1(255). That is true in sRGB space, but in linear space there this is non linear distribution. In any case, I have looked in the code - it converts the sampled pixel from image color space to scene linear color space. This works as expected, so will close the report.
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DH commented 2024-02-06 11:52:21 +01:00
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@iss Richard Antalik Hello, excuse me. But you are wrong. sRGB is transfered ColorSpace with gamma for displays to human eye perception. So sRGB is NON- linear.
and Linear space IS linear, so it has much more differentiation on high and low values. Instead sRGB is gamma-corrected, so it is a steep curve.
https://docs.krita.org/en/general_concepts/colors/linear_and_gamma.html

ImageE. means "Image Editor", ofc. There is also the "Sample Tool". Have you actually looked into the interfaces I mentioned?

But you know what, it's okay, its working and I found a solution to work with this. Just had to know that the Image Editor Sampling are the right sRGB values. But If I set sRGB in Color Management I assume I get everywhere in UI the same values.

EDIT: Sry you can close,

@iss Richard Antalik Hello, excuse me. But you are wrong. sRGB is transfered ColorSpace with gamma for displays to human eye perception. So sRGB is NON- linear. and Linear space IS linear, so it has much more differentiation on high and low values. Instead sRGB is gamma-corrected, so it is a steep curve. https://docs.krita.org/en/general_concepts/colors/linear_and_gamma.html ImageE. means "Image Editor", ofc. There is also the "Sample Tool". Have you actually looked into the interfaces I mentioned? But you know what, it's okay, its working and I found a solution to work with this. Just had to know that the Image Editor Sampling are the right sRGB values. But If I set sRGB in Color Management I assume I get everywhere in UI the same values. EDIT: Sry you can close,
DH reopened this issue 2024-02-06 11:52:28 +01:00
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DH closed this issue 2024-02-06 11:53:45 +01:00
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Richard Antalik commented 2024-02-06 14:15:26 +01:00
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@iss Richard Antalik Hello, excuse me. But you are wrong. sRGB is transfered ColorSpace with gamma for displays to human eye perception. So sRGB is NON- linear.
and Linear space IS linear, so it has much more differentiation on high and low values. Instead sRGB is gamma-corrected, so it is a steep curve.

I know that, what I meant is that if you transform linear progression (of numbers incrementyng by a constant) in sRGB to linear colorspace, you will end up in non-linear progression.

In any case I am not that familiar with conversion from one space to another, that I can just see, that it is wrong. But I have walked the code step by step and it has changed the sample value from 0.149019614 (sRGB) to 0.0193821695 by function IMB_colormanagement_colorspace_to_scene_linear_v3 with colorspace argument being sRGB. This conversion is done by OIIO library. Plugging numbers you provided to random online color converter also suggests that this behavior is correct.

In https://docs.blender.org/manual/en/latest/interface/controls/buttons/eyedropper.html they say, that this conversion is further influenced by view transform, which could explain your case, but that does not seem to be the case with my test case.

If you can provide sample .blend file so we are both looking at same colors, and the conversion is wrong I can reopen the report.

> @iss Richard Antalik Hello, excuse me. But you are wrong. sRGB is transfered ColorSpace with gamma for displays to human eye perception. So sRGB is NON- linear. > and Linear space IS linear, so it has much more differentiation on high and low values. Instead sRGB is gamma-corrected, so it is a steep curve. I know that, what I meant is that if you transform linear progression (of numbers incrementyng by a constant) in sRGB to linear colorspace, you will end up in non-linear progression. In any case I am not that familiar with conversion from one space to another, that I can just see, that it is wrong. But I have walked the code step by step and it has changed the sample value from 0.149019614 (sRGB) to 0.0193821695 by function `IMB_colormanagement_colorspace_to_scene_linear_v3` with colorspace argument being `sRGB`. This conversion is done by OIIO library. Plugging numbers you provided to random [online color converter](https://ajalt.github.io/colormath/converter/) also suggests that this behavior is correct. In https://docs.blender.org/manual/en/latest/interface/controls/buttons/eyedropper.html they say, that this conversion is further influenced by view transform, which could explain your case, but that does not seem to be the case with my test case. If you can provide sample .blend file so we are both looking at same colors, and the conversion is wrong I can reopen the report.
DH commented 2024-02-07 15:11:10 +01:00
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Okay, attached the file for comparison.

Okay, then it is not a bug. It converts correctly the values to "Linear sRGB", the Online Converter suggests.
Didn't know or forgot that Blender is always internal in "scene_linear".
I thought if I change in ColorManagement Display Device: sRGB & View Transform: Standard, the whole system works with this. But that actually doesn't change any values of the Colors in UI. Even you set another Display Device.

Excuse me this Information is Noted in the Manual for Color Picker, that the values are always as "scene_linear" respectively "Linear sRGB".
But maybe in ColorWindow an QoL option would be nice, to just show the Display Device e.g. sRGB values in the ColorWindows, even when they are converted internaly to "scene_linear". Otherwise you would need to think in two ColorSpaces.

Okay, attached the file for comparison. Okay, then it is **not** a bug. It converts correctly the values to "Linear sRGB", the Online Converter suggests. Didn't know or forgot that Blender is always internal in "scene_linear". I thought if I change in ColorManagement Display Device: sRGB & View Transform: Standard, the whole system works with this. But that actually doesn't change any values of the Colors in UI. Even you set another Display Device. Excuse me this Information is Noted in the Manual for [Color Picker](https://docs.blender.org/manual/en/dev/interface/controls/templates/color_picker.html), that the values are always as "scene_linear" respectively "Linear sRGB". But maybe in ColorWindow an QoL option would be nice, to just show the Display Device e.g. sRGB values in the ColorWindows, even when they are converted internaly to "scene_linear". Otherwise you would need to think in two ColorSpaces.
ImageEditor_to_ObjectColor_with_ColorPicker.blend
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