Saving grayscale images involves only red channel data from RGB. #103728

New Issue

Cassidy Graces Incandela · 2023-01-08T07:04:35+01:00

2023-01-08 07:04:35 +01:00

System Information
Operating system: Windows-10-10.0.19044-SP0 64 Bits
Graphics card: AMD Radeon(TM) R5 Graphics ATI Technologies Inc. 4.5.14831 Core Profile Context 21.5.2 27.20.21003.8013

Blender Version
Broken: version: 3.4.1, branch: blender-v3.4-release, commit date: 2022-12-19 17:00, hash: 55485cb379
Worked: (pretty sure this has been the case for a while)

Short description of error
Grayscale (BW) image output mode only takes data from the Red channel from RGB data instead of Value from HSV, omitting other data.

Exact steps for others to reproduce the error

Start a new project,
Construct three text objects,
Arrange their positions to make it more comfortable for you to observe,
For each three go to edit mode and write Red, Green, Blue respectively,
For each three add a new material with Emission shader for the surfaces, and set color hex code to #FF0000, #00FF00, #0000FF respectively,
To the properties area, go to Output Properties > Output, set Color to BW,
Render,
Open the rendered image in an image editor.

This is only to make it easy to notice the problem. You can use any scene or images and skip to step 6.

If you follow the steps above, you can observe that only the text Red is in the picture.
If you set a little bit of red for the others, e.g., #50FF00 for the Green, that text will be visible in the picture, with lower visibility.

I believe this is not how it is supposed to work, therefore I believe this is a bug. But the solution is probably going to involve additional processing before encoding, therefore it is going to be a bit slower. If that is not affordable, that is understandable, go ahead and close this report.

**System Information** Operating system: Windows-10-10.0.19044-SP0 64 Bits Graphics card: AMD Radeon(TM) R5 Graphics ATI Technologies Inc. 4.5.14831 Core Profile Context 21.5.2 27.20.21003.8013 **Blender Version** Broken: version: 3.4.1, branch: blender-v3.4-release, commit date: 2022-12-19 17:00, hash: 55485cb379 Worked: (pretty sure this has been the case for a while) **Short description of error** Grayscale (BW) image output mode only takes data from the Red channel from RGB data instead of Value from HSV, omitting other data. **Exact steps for others to reproduce the error** - Start a new project, - Construct three text objects, - Arrange their positions to make it more comfortable for you to observe, - For each three go to edit mode and write `Red`, `Green`, `Blue` respectively, - For each three add a new material with Emission shader for the surfaces, and set color hex code to `#FF0000`, `#00FF00`, `#0000FF` respectively, - To the properties area, go to `Output Properties > Output`, set `Color` to `BW`, - Render, - Open the rendered image in an image editor. > This is only to make it easy to notice the problem. You can use any scene or images and skip to step 6. If you follow the steps above, you can observe that only the text `Red` is in the picture. If you set a little bit of red for the others, e.g., `#50FF00` for the `Green`, that text will be visible in the picture, with lower visibility. I believe this is not how it is supposed to work, therefore I believe this is a bug. But the solution is probably going to involve additional processing before encoding, therefore it is going to be a bit slower. If that is not affordable, that is understandable, go ahead and close this report.

Cassidy Graces Incandela commented

2023-01-08 07:04:35 +01:00

Added subscriber: @cassidy

Cassidy Graces Incandela commented

2023-01-08 07:08:42 +01:00

Here is an example of the problem, and a workaround.
Workaround for this is by replacing the red channel from RGB by value data from HSV, or better yet, using the RGB to BW node to address our retina's various sensitivity to various wavelengths, and using the result to replace the red channel.

Render Layer	Separate Color - Value	RGB to BW (more accurate)

You can see an example of what I mentioned in the task description:

If you set a little bit of red for the others, e.g., #50FF00 for the Green, that text will be visible in the picture, with lower visibility.

There's a little bit of red in the Render Layer, and as a result, the text green can be seen.

Here is an example of the problem, and a workaround. Workaround for this is by replacing the red channel from RGB by value data from HSV, or better yet, using the `RGB to BW` node to address our retina's various sensitivity to various wavelengths, and using the result to replace the red channel. | **Render Layer** | **Separate Color - Value** | **RGB to BW** (more accurate) | | -- | -- | -- | | ![rgb.png](https://archive.blender.org/developer/F14131638/rgb.png) | ![workaround.png](https://archive.blender.org/developer/F14131678/workaround.png) | ![workaround-node.png](https://archive.blender.org/developer/F14131680/workaround-node.png) | | ![bw.png](https://archive.blender.org/developer/F14131641/bw.png) | ![bw-workaround.png](https://archive.blender.org/developer/F14131631/bw-workaround.png) | ![bw-workaround-node.png](https://archive.blender.org/developer/F14131633/bw-workaround-node.png) | You can see an example of what I mentioned in the task description: > If you set a little bit of red for the others, e.g., #50FF00 for the Green, that text will be visible in the picture, with lower visibility. There's a little bit of red in the Render Layer, and as a result, the text `green` can be seen.

Germano Cavalcante commented

2023-01-09 21:08:07 +01:00

Added subscriber: @mano-wii

Germano Cavalcante commented

2023-01-09 21:08:07 +01:00

Changed status from 'Needs Triage' to: 'Archived'

Germano Cavalcante closed this issue

2023-01-09 21:08:07 +01:00

Germano Cavalcante commented

2023-01-09 21:08:07 +01:00

This is part of the PNG implementation in Blender: {https://developer.blender.org/diffusion/B/browse/master/source/blender/imbuf/intern/png.c$371-374}

It exists before what we can trace in this channel: {https://developer.blender.org/diffusion/B/browse/master/source/blender/imbuf/intern/png_encode.c;12315f4d0e0ae993805f141f64cb8c73c5297311?follow=first}

Works as designed and is therefore not considered a bug.

So thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors.

For user requests and feedback, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests

For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

This is part of the PNG implementation in Blender: {https://developer.blender.org/diffusion/B/browse/master/source/blender/imbuf/intern/png.c$371-374} It exists before what we can trace in this channel: {https://developer.blender.org/diffusion/B/browse/master/source/blender/imbuf/intern/png_encode.c;12315f4d0e0ae993805f141f64cb8c73c5297311?follow=first} Works as designed and is therefore not considered a bug. So thanks for the report, but the issue reported here is a request for modified/improved behavior and not a bug in current behavior. Closing as this bug tracker is only for bugs and errors. For user requests and feedback, please use other channels: https://wiki.blender.org/wiki/Communication/Contact#User_Feedback_and_Requests For more information on why this isn't considered a bug, visit: https://wiki.blender.org/wiki/Reference/Not_a_bug

Jesse Yurkovich referenced a pull request that will close this issue

2023-03-21 19:25:17 +01:00

Image: Use OpenImageIO for loading and saving a variety of image formats #105785

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Saving grayscale images involves only red channel data from RGB. #103728