TextureTools namespace
Texture tools.
Contents
- Reference
Tools for generating, compressing and optimizing textures.
This library is built if WITH_TEXTURETOOLS is enabled when building Magnum. To use this library with CMake, you need to request the TextureTools component of the Magnum package in CMake and link to the Magnum::TextureTools target:
find_package(Magnum REQUIRED TextureTools) # ... target_link_libraries(your-app Magnum::TextureTools)
Note that functionality depending on GL APIs is available only if Magnum is built with both WITH_GL and TARGET_GL enabled (which is done by default).
See Downloading and building and Usage with CMake for more information.
Functions
-
auto atlas(const Vector2i& atlasSize,
const std::
vector<Vector2i>& sizes, const Vector2i& padding = Vector2i()) -> std:: vector<Range2Di> - Pack textures into texture atlas.
-
void distanceField(GL::
Texture2D& input, GL:: Texture2D& output, const Range2Di& rectangle, Int radius, const Vector2i& imageSize = Vector2i()) - Create signed distance field.
Function documentation
std::
Pack textures into texture atlas.
| Parameters | |
|---|---|
| atlasSize | Size of resulting atlas |
| sizes | Sizes of all textures in the atlas |
| padding | Padding around each texture |
Packs many small textures into one larger. If the textures cannot be packed into required size, empty vector is returned.
Padding is added twice to each size and the atlas is laid out so the padding don't overlap. Returned sizes are the same as original sizes, i.e. without the padding.
void Magnum::
Create signed distance field.
| Parameters | |
|---|---|
| input | Input texture |
| output | Output texture |
| rectangle | Rectangle in output texture where to render |
| radius | Max lookup radius in input texture |
| imageSize | Input texture size. Needed only in OpenGL ES, in desktop OpenGL the information is gathered automatically using GL:: |
Converts binary image (stored in red channel of input) to signed distance field (stored in red channel in rectangle of output). The purpose of this function is to convert high-resolution binary image (such as vector artwork or font glyphs) to low-resolution grayscale image. The image will then occupy much less memory and can be scaled without aliasing issues. Additionally it provides foundation for features like outlining, glow or drop shadow essentially for free.
You can also use the magnum-distancefieldconverter utility to do distance field conversion on command-line. By extension, this functionality is also provided through magnum-fontconverter utility.
The algorithm
For each pixel inside rectangle the algorithm looks at corresponding pixel in input and tries to find nearest pixel of opposite color in area given by radius. Signed distance between the points is then saved as value of given pixel in output. Value of 1.0 means that the pixel was originally colored white and nearest black pixel is farther than radius, value of 0.0 means that the pixel was originally black and nearest white pixel is farther than radius. Values around 0.5 are around edges.
The resulting texture can be used with bilinear filtering. It can be converted back to binary form in shader using e.g. GLSL smoothstep() function with step around 0.5 to create antialiased edges. Or you can exploit the distance field features to create many other effects. See also Shaders::
Based on: Chris Green - Improved Alpha-Tested Magnification for Vector Textures and Special Effects, SIGGRAPH 2007, http://www.valvesoftware.com/publications/2007/SIGGRAPH2007_