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Semitransparent rendering bug in SRGB blending method #469

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opened 2024-12-21 19:35:42 -06:00 by SoprachevAK · 2 comments

SoprachevAK commented

2024-12-21 19:35:42 -06:00

(Migrated from github.com)

Operating System Info

Other

Other OS

macOS 15, Windows 10

OBS Studio Version

Other

OBS Studio Version (Other)

31.0.0, 30.2.3

OBS Studio Log URL

https://obsproject.com/logs/ZJw0Cy9mkJNEyV3i

OBS Studio Crash Log URL

No response

Expected Behavior

The OBS Browser Source should correctly render half transparent colors without darkening colors or introducing artifacts around edges.

Current Behavior

Half transparent pixels render darkened than actual should, and black artifacts are present around text (due anti aliasing, which produce half transparency)

Steps to Reproduce

Add white color background
Add this html page like Browser source with default CSS preset (transparent body background)

<html lang="en">
<body>
  <div style="
    margin: 0;
    font-size: 2em;
    font-weight: 900;
    font-family: monospace;
  ">
    <p style="color: #ffffff">#ffffff / 100%</p>
    <p style="color: rgb(255 255 255 / 75%)">#ffffff / 75%</p>
    <p style="color: rgb(255 255 255 / 25%)">#ffffff / 25%</p>
    <p style="color: #1e6ce080">#1e6ce0 / 50%</p>
  </div>
</body>
</html>

Switching Blending Method between Default and SRBG Off and see differences

Anything else we should know?

This artifacts looks like premultiplied RGBA rendering like non premultiplied

I am check rendering mechanism, and it correctly set blending mode for premultiplied renderer github.com/obsproject/obs-browser@082a0a2d1c/obs-browser-source.cpp (L646)

I try to play with srgb texture binding, and if set gs_enable_framebuffer_srgb(false); and gs_effect_set_texture(image, draw_texture) here:
github.com/obsproject/obs-browser@082a0a2d1c/obs-browser-source.cpp (L652)
All works correctly, but i think, that this code and linear_sample needed for something

I am interested in fixing this bug and can create a PR, but I need advice on which direction to take next.

### Operating System Info Other ### Other OS macOS 15, Windows 10 ### OBS Studio Version Other ### OBS Studio Version (Other) 31.0.0, 30.2.3 ### OBS Studio Log URL https://obsproject.com/logs/ZJw0Cy9mkJNEyV3i ### OBS Studio Crash Log URL _No response_ ### Expected Behavior The OBS Browser Source should correctly render half transparent colors without darkening colors or introducing artifacts around edges. <img width="364" alt="image" src="https://github.com/user-attachments/assets/aabff468-9b66-496d-9d51-358e22404c92" /> ### Current Behavior Half transparent pixels render darkened than actual should, and black artifacts are present around text (due anti aliasing, which produce half transparency) <img width="405" alt="image" src="https://github.com/user-attachments/assets/52a67010-ced8-4258-aea7-cf09da485528" /> ### Steps to Reproduce 1. Add white color background 2. Add this html page like `Browser` source with default `CSS` preset (transparent body background) ```html <html lang="en"> <body> <div style=" margin: 0; font-size: 2em; font-weight: 900; font-family: monospace; "> <p style="color: #ffffff">#ffffff / 100%</p> <p style="color: rgb(255 255 255 / 75%)">#ffffff / 75%</p> <p style="color: rgb(255 255 255 / 25%)">#ffffff / 25%</p> <p style="color: #1e6ce080">#1e6ce0 / 50%</p> </div> </body> </html> ``` 3. Switching `Blending Method` between `Default` and `SRBG Off` and see differences ### Anything else we should know? This artifacts looks like `premultiplied RGBA` rendering like `non premultiplied` I am check rendering mechanism, and it correctly set blending mode for premultiplied renderer https://github.com/obsproject/obs-browser/blob/082a0a2d1c393f66dc68b62fa402ca23d4c02dbe/obs-browser-source.cpp#L646 I try to play with srgb texture binding, and if set `gs_enable_framebuffer_srgb(false);` and `gs_effect_set_texture(image, draw_texture)` here: https://github.com/obsproject/obs-browser/blob/082a0a2d1c393f66dc68b62fa402ca23d4c02dbe/obs-browser-source.cpp#L652 All works correctly, but i think, that this code and `linear_sample` needed for something I am interested in fixing this bug and can create a PR, but I need advice on which direction to take next.

SoprachevAK commented

2024-12-21 19:42:18 -06:00

(Migrated from github.com)

May be srgb rendering mode overrides blend functions somewhere in rendering pipeline outside CEF

May be `srgb` rendering mode overrides blend functions somewhere in rendering pipeline outside CEF

SoprachevAK commented

2025-07-15 16:46:13 -05:00

(Migrated from github.com)

still reproduced

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Reference

gh-obsproject/obs-browser#469

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