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Along with the bits in Text library this is one of the last things that still assume OpenGL present by default. As usual, the old name and header is now a deprecated typedef.pull/650/head
Vladimír Vondruš
2 years ago
13 changed files with 283 additions and 217 deletions
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#ifndef Magnum_TextureTools_DistanceFieldGL_h |
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#define Magnum_TextureTools_DistanceFieldGL_h |
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/*
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This file is part of Magnum. |
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Copyright © 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018, 2019, |
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2020, 2021, 2022, 2023 Vladimír Vondruš <mosra@centrum.cz> |
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Permission is hereby granted, free of charge, to any person obtaining a |
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copy of this software and associated documentation files (the "Software"), |
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to deal in the Software without restriction, including without limitation |
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the rights to use, copy, modify, merge, publish, distribute, sublicense, |
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and/or sell copies of the Software, and to permit persons to whom the |
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Software is furnished to do so, subject to the following conditions: |
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The above copyright notice and this permission notice shall be included |
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in all copies or substantial portions of the Software. |
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL |
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THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER |
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DEALINGS IN THE SOFTWARE. |
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*/ |
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/** @file
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* @brief Class @ref Magnum::TextureTools::DistanceFieldGL |
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*/ |
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#include "Magnum/configure.h" |
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#ifdef MAGNUM_TARGET_GL |
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#include <Corrade/Containers/Pointer.h> |
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#include "Magnum/Magnum.h" |
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#include "Magnum/GL/GL.h" |
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#ifndef MAGNUM_TARGET_GLES |
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#include "Magnum/Math/Vector2.h" |
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#endif |
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#include "Magnum/TextureTools/visibility.h" |
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namespace Magnum { namespace TextureTools { |
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/**
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@brief Create a signed distance field using OpenGL |
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Converts a binary black/white image (stored in the red channel of @p input) to |
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a signed distance field (stored in the red channel of @p output @p rectangle). |
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The purpose of this function is to convert a high-resolution binary image (such |
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as vector artwork or font glyphs) to a low-resolution grayscale image. The |
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image will then occupy much less memory and can be scaled without aliasing |
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issues. Additionally it provides foundation for features like outlining, glow |
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or drop shadow essentially for free. |
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You can also use the @ref magnum-distancefieldconverter "magnum-distancefieldconverter" |
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utility to do distance field conversion on command-line. This functionality is |
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also used inside the @ref magnum-fontconverter "magnum-fontconverter" utility. |
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@section TextureTools-DistanceFieldGL-algorithm The algorithm |
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For each pixel inside the @p output sub-rectangle the algorithm looks at |
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corresponding pixel in the input and tries to find nearest pixel of opposite |
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color in an area defined @p radius. Signed distance between the points is then |
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saved as value of given pixel in @p output. Value of 1.0 means that the pixel |
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was originally colored white and nearest black pixel is farther than @p radius, |
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value of 0.0 means that the pixel was originally black and nearest white pixel |
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is farther than @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 @glsl smoothstep() @ce function |
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with step around 0.5 to create antialiased edges. Or you can exploit the |
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distance field features to create many other effects. See also |
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@ref Shaders::DistanceFieldVectorGL. |
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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 a GPU-only implementation, so it expects an active GL |
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context. |
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@note This function is available only if Magnum is compiled with |
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@ref MAGNUM_TARGET_GL enabled (done by default). See @ref building-features |
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for more information. |
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*/ |
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class MAGNUM_TEXTURETOOLS_EXPORT DistanceFieldGL { |
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public: |
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/**
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* @brief Constructor |
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* @param radius Max lookup radius in the input texture |
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* |
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* Prepares the shader and other internal state for given @p radius. |
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*/ |
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explicit DistanceFieldGL(UnsignedInt radius); |
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/**
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* @brief Construct without creating the internal OpenGL state |
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* @m_since_latest |
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* |
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* The constructed instance is equivalent to moved-from state, i.e. no |
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* APIs can be safely called on the object. Useful in cases where you |
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* will overwrite the instance later anyway. Move another object over |
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* it to make it useful. |
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* |
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* This function can be safely used for constructing (and later |
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* destructing) objects even without any OpenGL context being active. |
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* However note that this is a low-level and a potentially dangerous |
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* API, see the documentation of @ref NoCreate for alternatives. |
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*/ |
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explicit DistanceFieldGL(NoCreateT) noexcept; |
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/** @brief Copying is not allowed */ |
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DistanceFieldGL(const DistanceFieldGL&) = delete; |
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/**
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* @brief Move constructor |
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* @m_since_latest |
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* |
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* Performs a destructive move, i.e. the original object isn't usable |
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* afterwards anymore. |
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*/ |
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DistanceFieldGL(DistanceFieldGL&&) noexcept; |
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~DistanceFieldGL(); |
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/** @brief Copying is not allowed */ |
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DistanceFieldGL& operator=(const DistanceFieldGL&) = delete; |
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/** @brief Move constructor */ |
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DistanceFieldGL& operator=(DistanceFieldGL&&) noexcept; |
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/** @brief Max lookup radius */ |
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UnsignedInt radius() const; |
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/**
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* @brief Calculate the distance field to a framebuffer |
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* @param input Input texture |
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* @param output Output framebuffer |
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* @param rectangle Rectangle in output texture where to render |
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* @param imageSize Input texture size. Needed only for OpenGL ES, |
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* on desktop GL the information is gathered automatically using |
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* @ref GL::Texture2D::imageSize(). |
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* @m_since_latest |
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* |
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* The @p output texture is expected to have a framebuffer-drawable |
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* @ref GL::TextureFormat. On desktop OpenGL and |
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* OpenGL ES 3.0 it's common to render to @ref GL::TextureFormat::R8. |
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* On OpenGL ES 2.0 you can use @ref GL::TextureFormat::Red if |
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* @gl_extension{EXT,texture_rg} is available; if not, the smallest but |
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* still inefficient supported format is in most cases |
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* @ref GL::TextureFormat::RGB. The @ref GL::TextureFormat::Luminance |
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* format usually isn't renderable. |
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* |
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* Additionally, the ratio of the @p input size (or @p imageSize on |
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* OpenGL ES) and @p rectangle size is expected to be a multiple of 2, |
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* as that's what the generator shader relies on for correct pixel |
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* addressing. |
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*/ |
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void operator()(GL::Texture2D& input, GL::Framebuffer& output, const Range2Di& rectangle, const Vector2i& imageSize |
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#ifndef MAGNUM_TARGET_GLES |
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= {} |
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#endif |
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); |
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/**
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* @brief Calculate the distance field to a texture |
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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 imageSize Input texture size. Needed only for OpenGL ES, |
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* on desktop GL the information is gathered automatically using |
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* @ref GL::Texture2D::imageSize(). |
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* |
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* Creates a framebuffer with @p output attached and calls |
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* @ref operator()(GL::Texture2D&, GL::Framebuffer&, const Range2Di&, const Vector2i&). |
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*/ |
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void operator()(GL::Texture2D& input, GL::Texture2D& output, const Range2Di& rectangle, const Vector2i& imageSize |
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#ifndef MAGNUM_TARGET_GLES |
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= {} |
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#endif |
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); |
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private: |
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struct State; |
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Containers::Pointer<State> _state; |
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}; |
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}} |
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#else |
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#error this header is available only in the OpenGL build |
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#endif |
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#endif |
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