75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
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/*
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* Copyright 2020 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#ifndef SkImageSampling_DEFINED
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#define SkImageSampling_DEFINED
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#include "include/core/SkTypes.h"
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enum class SkSamplingMode {
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kNearest, // single sample point (nearest neighbor)
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kLinear, // interporate between 2x2 sample points (bilinear interpolation)
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};
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enum class SkMipmapMode {
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kNone, // ignore mipmap levels, sample from the "base"
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kNearest, // sample from the nearest level
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kLinear, // interpolate between the two nearest levels
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};
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/*
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* Specify B and C (each between 0...1) to create a shader that applies the corresponding
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* cubic reconstruction filter to the image.
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*
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* Example values:
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* B = 1/3, C = 1/3 "Mitchell" filter
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* B = 0, C = 1/2 "Catmull-Rom" filter
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*
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* See "Reconstruction Filters in Computer Graphics"
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* Don P. Mitchell
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* Arun N. Netravali
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* 1988
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* https://www.cs.utexas.edu/~fussell/courses/cs384g-fall2013/lectures/mitchell/Mitchell.pdf
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*
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* Desmos worksheet https://www.desmos.com/calculator/aghdpicrvr
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* Nice overview https://entropymine.com/imageworsener/bicubic/
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*/
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struct SkCubicResampler {
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float B, C;
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};
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struct SkFilterOptions {
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SkSamplingMode fSampling;
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SkMipmapMode fMipmap;
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};
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struct SkSamplingOptions {
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bool fUseCubic;
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SkCubicResampler fCubic; //!< use if fUseCubic is true
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SkFilterOptions fFilter; //!< use if fUseCubic is false
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SkSamplingOptions()
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: fUseCubic(false)
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, fCubic({0,0})
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, fFilter({SkSamplingMode::kNearest, SkMipmapMode::kNone})
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{}
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SkSamplingOptions(const SkFilterOptions& filter)
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: fUseCubic(false)
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, fCubic({0,0}) // ignored
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, fFilter(filter)
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{}
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SkSamplingOptions(const SkCubicResampler& cubic)
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: fUseCubic(true)
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, fCubic(cubic)
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, fFilter({SkSamplingMode::kNearest, SkMipmapMode::kNone}) // ignored
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{}
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};
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#endif
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