/src/skia/include/core/SkSamplingOptions.h
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1 | | /* |
2 | | * Copyright 2020 Google Inc. |
3 | | * |
4 | | * Use of this source code is governed by a BSD-style license that can be |
5 | | * found in the LICENSE file. |
6 | | */ |
7 | | |
8 | | #ifndef SkImageSampling_DEFINED |
9 | | #define SkImageSampling_DEFINED |
10 | | |
11 | | #include "include/core/SkTypes.h" |
12 | | #include <new> |
13 | | |
14 | | enum class SkFilterMode { |
15 | | kNearest, // single sample point (nearest neighbor) |
16 | | kLinear, // interporate between 2x2 sample points (bilinear interpolation) |
17 | | |
18 | | kLast = kLinear, |
19 | | }; |
20 | | |
21 | | enum class SkMipmapMode { |
22 | | kNone, // ignore mipmap levels, sample from the "base" |
23 | | kNearest, // sample from the nearest level |
24 | | kLinear, // interpolate between the two nearest levels |
25 | | |
26 | | kLast = kLinear, |
27 | | }; |
28 | | |
29 | | /* |
30 | | * Specify B and C (each between 0...1) to create a shader that applies the corresponding |
31 | | * cubic reconstruction filter to the image. |
32 | | * |
33 | | * Example values: |
34 | | * B = 1/3, C = 1/3 "Mitchell" filter |
35 | | * B = 0, C = 1/2 "Catmull-Rom" filter |
36 | | * |
37 | | * See "Reconstruction Filters in Computer Graphics" |
38 | | * Don P. Mitchell |
39 | | * Arun N. Netravali |
40 | | * 1988 |
41 | | * https://www.cs.utexas.edu/~fussell/courses/cs384g-fall2013/lectures/mitchell/Mitchell.pdf |
42 | | * |
43 | | * Desmos worksheet https://www.desmos.com/calculator/aghdpicrvr |
44 | | * Nice overview https://entropymine.com/imageworsener/bicubic/ |
45 | | */ |
46 | | struct SkCubicResampler { |
47 | | float B, C; |
48 | | |
49 | | // Historic default for kHigh_SkFilterQuality |
50 | 0 | static constexpr SkCubicResampler Mitchell() { return {1/3.0f, 1/3.0f}; } |
51 | 0 | static constexpr SkCubicResampler CatmullRom() { return {0.0f, 1/2.0f}; } |
52 | | }; |
53 | | |
54 | | struct SK_API SkSamplingOptions { |
55 | | const bool useCubic = false; |
56 | | const SkCubicResampler cubic = {0, 0}; |
57 | | const SkFilterMode filter = SkFilterMode::kNearest; |
58 | | const SkMipmapMode mipmap = SkMipmapMode::kNone; |
59 | | |
60 | 165k | SkSamplingOptions() = default; |
61 | | SkSamplingOptions(const SkSamplingOptions&) = default; |
62 | 9.18k | SkSamplingOptions& operator=(const SkSamplingOptions& that) { |
63 | 9.18k | this->~SkSamplingOptions(); // A pedantic no-op. |
64 | 9.18k | new (this) SkSamplingOptions(that); |
65 | 9.18k | return *this; |
66 | 9.18k | } |
67 | | |
68 | | SkSamplingOptions(SkFilterMode fm, SkMipmapMode mm) |
69 | | : useCubic(false) |
70 | | , filter(fm) |
71 | 15.8k | , mipmap(mm) {} |
72 | | |
73 | | explicit SkSamplingOptions(SkFilterMode fm) |
74 | | : useCubic(false) |
75 | | , filter(fm) |
76 | 22.2k | , mipmap(SkMipmapMode::kNone) {} |
77 | | |
78 | | explicit SkSamplingOptions(const SkCubicResampler& c) |
79 | | : useCubic(true) |
80 | 4.82k | , cubic(c) {} |
81 | | |
82 | 2.07k | bool operator==(const SkSamplingOptions& other) const { |
83 | 2.07k | return useCubic == other.useCubic |
84 | 1.37k | && cubic.B == other.cubic.B |
85 | 1.37k | && cubic.C == other.cubic.C |
86 | 1.37k | && filter == other.filter |
87 | 663 | && mipmap == other.mipmap; |
88 | 2.07k | } |
89 | 2.07k | bool operator!=(const SkSamplingOptions& other) const { return !(*this == other); } |
90 | | }; |
91 | | |
92 | | #endif |