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65 lines
2.8 KiB
65 lines
2.8 KiB
#ifndef Magnum_TextureTools_DistanceField_h |
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#define Magnum_TextureTools_DistanceField_h |
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/* |
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Copyright © 2010, 2011, 2012 Vladimír Vondruš <mosra@centrum.cz> |
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This file is part of Magnum. |
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Magnum is free software: you can redistribute it and/or modify |
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it under the terms of the GNU Lesser General Public License version 3 |
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only, as published by the Free Software Foundation. |
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Magnum is distributed in the hope that it will be useful, |
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but WITHOUT ANY WARRANTY; without even the implied warranty of |
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
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GNU Lesser General Public License version 3 for more details. |
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*/ |
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/** @file |
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* @brief Function Magnum::TextureTools::distanceField() |
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*/ |
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#include "Magnum.h" |
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#include "TextureTools/magnumTextureToolsVisibility.h" |
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namespace Magnum { namespace TextureTools { |
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/** |
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@brief Create signed distance field |
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@param input Input texture |
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@param output Output texture |
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@param rectangle Rectangle in output texture where to render |
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@param radius Max lookup radius in input texture |
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Converts binary image (stored in red channel of @p input) to signed distance |
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field (stored in red channel in @p rectangle of @p output). The purpose of this |
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function is to convert high-resolution binary image (such as vector artwork or |
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font glyphs) to low-resolution grayscale image. The image will then occupy much |
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less memory and can be scaled without aliasing issues. Additionally it provides |
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foundation for features like outlining, glow or drop shadow essentialy for free. |
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For each pixel inside @p rectangle the algorithm looks at corresponding pixel in |
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@p input and tries to find nearest pixel of opposite color in area given by |
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@p radius. Signed distance between the points is then saved as value of given |
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pixel in @p output. Value of `0` means that the pixel was originally colored |
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white and nearest black pixel is farther than @p radius, value of `1` means that |
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the pixel was originally black and nearest white pixel is farther than |
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@p radius. Values around `0.5` are around edges. |
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The resulting texture can be used with bilinear filtering. It can be converted |
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back to binary form in shader using e.g. GLSL `smoothstep()` function with step |
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around `0.5` to create antialiased edges. Or you can exploit the distance field |
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features to create many other effects. See also Shaders::DistanceFieldVectorShader. |
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Based on: *Chris Green - Improved Alpha-Tested Magnification for Vector Textures |
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and Special Effects, SIGGRAPH 2007, |
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http://www.valvesoftware.com/publications/2007/SIGGRAPH2007_AlphaTestedMagnification.pdf* |
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@attention This is GPU-only implementation, so it expects active context. |
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*/ |
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void MAGNUM_TEXTURETOOLS_EXPORT distanceField(Texture2D* input, Texture2D* output, const Rectanglei& rectangle, const Int radius); |
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}} |
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#endif
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