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imgui_freetype: comments about correct blending and sRGB (#618, #578)

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This commit is contained in:
omar 2018-02-05 11:21:06 +01:00
parent a33b86dac7
commit cf6b39600b
2 changed files with 12 additions and 0 deletions
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6
misc/freetype/README.md
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@ -17,6 +17,12 @@ ImGuiFreeType::BuildFontAtlas(io.Fonts, flags);
io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);
```
**Gamma Correct Blending**
FreeType assumes blending in linear space rather than gamma space.
See FreeType note for [FT_Render_Glyph](https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Render_Glyph).
For correct results you need to be using sRGB and convert to linear space in the pixel shader output.
The default imgui styles will be impacted by this change (alpha values will need tweaking).
**Test code Usage**
```cpp
#include "misc/freetype/imgui_freetype.h"

6
misc/freetype/imgui_freetype.cpp
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@ -10,6 +10,12 @@
// - v0.54: (2018/01/22) fix for addition of ImFontAtlas::TexUvscale member
// - v0.55: (2018/02/04) moved to main imgui repository (away from http://www.github.com/ocornut/imgui_club)
// Gamma Correct Blending:
// FreeType assumes blending in linear space rather than gamma space.
// See https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Render_Glyph
// For correct results you need to be using sRGB and convert to linear space in the pixel shader output.
// The default imgui styles will be impacted by this change (alpha values will need tweaking).
// TODO:
// - Output texture has excessive resolution (lots of vertical waste)
// - FreeType's memory allocator is not overridden.