Image editor shows color banding on rendered images (even with dither set to 2.0) #35074

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Ben Thery · 2013-04-25T10:13:46+02:00

Ben Thery commented

2013-04-25 10:13:46 +02:00

%%%--- Operating System, Graphics card ---

Seen on two systems:

Linux Mint 13 / nVidia Quadro FX 570 256MB
Linux Ubuntu 12.10 / AMD Radeon HD 4770 512MB
- Blender version with error, and version that worked ---
Broken in 2.67 svn
Good in 2.66a
- Short description of error ---

When rendering a scene, the resulting image displayed in the image editor shows color banding even when dithering is activated.
It is as if dithering is not taken into account anymore.
But it is not the case. Indeed, it is only a display error because the rendered image when saved to file (.png) doesn't show any color banding in an external image viewer.

- Steps for others to reproduce the error (preferably based on attached .blend file) ---

With both 2.66a and 2.67svn do:

Use default scene
In the "Render" panel, "Post-Processing" properties, set "Dither" to 2.0
In the "World" panel, check the "Blend Sky" checkbox (keep default colors)
Render
In Blender 2.66a, rendered image background is clean/nice, no banding

  In Blender 2.67svn, in the image editor the rendered image shows heavy color banding in the background

 If you save the render, the saved image doesn't have the banding.

See attachements:

Inside Blender, with color banding
Saved rendered image, no banding

%%%

%%%--- Operating System, Graphics card --- Seen on two systems: - Linux Mint 13 / nVidia Quadro FX 570 256MB - Linux Ubuntu 12.10 / AMD Radeon HD 4770 512MB - Blender version with error, and version that worked --- - Broken in 2.67 svn - Good in 2.66a - Short description of error --- When rendering a scene, the resulting image displayed in the image editor shows color banding even when dithering is activated. It is as if dithering is not taken into account anymore. But it is not the case. Indeed, it is only a display error because the rendered image when saved to file (.png) doesn't show any color banding in an external image viewer. - Steps for others to reproduce the error (preferably based on attached .blend file) --- With both 2.66a and 2.67svn do: 1. Use default scene 2. In the "Render" panel, "Post-Processing" properties, set "Dither" to 2.0 3. In the "World" panel, check the "Blend Sky" checkbox (keep default colors) 4. Render 5. In Blender 2.66a, rendered image background is clean/nice, no banding ``` In Blender 2.67svn, in the image editor the rendered image shows heavy color banding in the background ``` ``` If you save the render, the saved image doesn't have the banding. ``` See attachements: - Inside Blender, with color banding - Saved rendered image, no banding %%%

Ben Thery commented

2013-04-25 10:13:46 +02:00

Changed status to: 'Open'

Campbell Barton commented

2013-04-25 12:57:14 +02:00

%%%I can't redo this bug,
With opencolorio enabled or disabled at compile time, its dithering.

source/blender/imbuf/intern/divers.c, dither_value, try change..

di->v- [x] = v_in + (2 * di->v- [x] + di->e- [x]) * di->f;

to

di->v- [x] = v_in + (2 * di->v- [x] + di->e- [x]) * (di->f * 20.0f);

assigning to sergey.%%%

%%%I can't redo this bug, With opencolorio enabled or disabled at compile time, its dithering. source/blender/imbuf/intern/divers.c, dither_value, try change.. di->v- [x] = v_in + (2 * di->v- [x] + di->e- [x]) * di->f; to di->v- [x] = v_in + (2 * di->v- [x] + di->e- [x]) * (di->f * 20.0f); assigning to sergey.%%%

Sergey Sharybin commented

2013-04-25 14:04:32 +02:00

%%%Fixed dither issue in svn rev56291.

There'll be some banding when not using dither, but that's also how it was in 2.66a and not sure if it's even solvable -- more a limitation of 8bit display.

Anyway, thanks for the report and please let me know if you'll notice more issues.%%%

%%%Fixed dither issue in svn rev56291. There'll be some banding when not using dither, but that's also how it was in 2.66a and not sure if it's even solvable -- more a limitation of 8bit display. Anyway, thanks for the report and please let me know if you'll notice more issues.%%%

Sergey Sharybin commented

2013-04-25 14:04:33 +02:00

Changed status from 'Open' to: 'Resolved'

Sergey Sharybin closed this issue

2013-04-25 14:04:33 +02:00

Ben Thery commented

2013-04-25 19:31:06 +02:00

%%%I confirm it is fixed for me: No color banding anymore with dithering (back to 2.66a behaviour).

Thank you Sergey.%%%

%%%I confirm it is fixed for me: No color banding anymore with dithering (back to 2.66a behaviour). Thank you Sergey.%%%

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Reference: blender/blender#35074

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Image editor shows color banding on rendered images (even with dither set to 2.0) #35074