humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 1 | /* |
| 2 | * Copyright 2013 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 | |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 8 | #ifndef SkBitmapFilter_DEFINED |
| 9 | #define SkBitmapFilter_DEFINED |
| 10 | |
bungeman | d3ebb48 | 2015-08-05 13:57:49 -0700 | [diff] [blame] | 11 | #include "SkFixed.h" |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 12 | #include "SkMath.h" |
bungeman | d3ebb48 | 2015-08-05 13:57:49 -0700 | [diff] [blame] | 13 | #include "SkScalar.h" |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 14 | |
| 15 | // size of the precomputed bitmap filter tables for high quality filtering. |
| 16 | // Used to precompute the shape of the filter kernel. |
| 17 | // Table size chosen from experiments to see where I could start to see a difference. |
| 18 | |
humper@google.com | 87fbf4f | 2013-07-10 21:49:29 +0000 | [diff] [blame] | 19 | #define SKBITMAP_FILTER_TABLE_SIZE 128 |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 20 | |
| 21 | class SkBitmapFilter { |
| 22 | public: |
| 23 | SkBitmapFilter(float width) |
| 24 | : fWidth(width), fInvWidth(1.f/width) { |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 25 | fPrecomputed = false; |
| 26 | fLookupMultiplier = this->invWidth() * (SKBITMAP_FILTER_TABLE_SIZE-1); |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 27 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 28 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 29 | SkFixed lookup(float x) const { |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 30 | if (!fPrecomputed) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 31 | precomputeTable(); |
| 32 | } |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 33 | int filter_idx = int(sk_float_abs(x * fLookupMultiplier)); |
| 34 | SkASSERT(filter_idx < SKBITMAP_FILTER_TABLE_SIZE); |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 35 | return fFilterTable[filter_idx]; |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 36 | } |
| 37 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 38 | SkScalar lookupScalar(float x) const { |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 39 | if (!fPrecomputed) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 40 | precomputeTable(); |
| 41 | } |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 42 | int filter_idx = int(sk_float_abs(x * fLookupMultiplier)); |
| 43 | SkASSERT(filter_idx < SKBITMAP_FILTER_TABLE_SIZE); |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 44 | return fFilterTableScalar[filter_idx]; |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 45 | } |
| 46 | |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 47 | float width() const { return fWidth; } |
| 48 | float invWidth() const { return fInvWidth; } |
| 49 | virtual float evaluate(float x) const = 0; |
| 50 | virtual ~SkBitmapFilter() {} |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 51 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 52 | static SkBitmapFilter* Allocate(); |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 53 | protected: |
| 54 | float fWidth; |
| 55 | float fInvWidth; |
skia.committer@gmail.com | fa1bd5f | 2013-07-13 07:00:56 +0000 | [diff] [blame] | 56 | |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 57 | float fLookupMultiplier; |
| 58 | |
| 59 | mutable bool fPrecomputed; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 60 | mutable SkFixed fFilterTable[SKBITMAP_FILTER_TABLE_SIZE]; |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 61 | mutable SkScalar fFilterTableScalar[SKBITMAP_FILTER_TABLE_SIZE]; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 62 | private: |
| 63 | void precomputeTable() const { |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 64 | fPrecomputed = true; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 65 | SkFixed *ftp = fFilterTable; |
humper@google.com | 9c96d4b | 2013-07-14 01:44:59 +0000 | [diff] [blame] | 66 | SkScalar *ftpScalar = fFilterTableScalar; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 67 | for (int x = 0; x < SKBITMAP_FILTER_TABLE_SIZE; ++x) { |
| 68 | float fx = ((float)x + .5f) * this->width() / SKBITMAP_FILTER_TABLE_SIZE; |
| 69 | float filter_value = evaluate(fx); |
commit-bot@chromium.org | 4b413c8 | 2013-11-25 19:44:07 +0000 | [diff] [blame] | 70 | *ftpScalar++ = filter_value; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 71 | *ftp++ = SkFloatToFixed(filter_value); |
| 72 | } |
| 73 | } |
| 74 | }; |
| 75 | |
| 76 | class SkMitchellFilter: public SkBitmapFilter { |
| 77 | public: |
| 78 | SkMitchellFilter(float b, float c, float width=2.0f) |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 79 | : SkBitmapFilter(width), B(b), C(c) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 80 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 81 | |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 82 | float evaluate(float x) const override { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 83 | x = fabsf(x); |
| 84 | if (x > 2.f) { |
| 85 | return 0; |
| 86 | } else if (x > 1.f) { |
| 87 | return ((-B - 6*C) * x*x*x + (6*B + 30*C) * x*x + |
| 88 | (-12*B - 48*C) * x + (8*B + 24*C)) * (1.f/6.f); |
| 89 | } else { |
| 90 | return ((12 - 9*B - 6*C) * x*x*x + |
| 91 | (-18 + 12*B + 6*C) * x*x + |
| 92 | (6 - 2*B)) * (1.f/6.f); |
| 93 | } |
| 94 | } |
| 95 | protected: |
| 96 | float B, C; |
| 97 | }; |
| 98 | |
| 99 | class SkGaussianFilter: public SkBitmapFilter { |
| 100 | public: |
| 101 | SkGaussianFilter(float a, float width=2.0f) |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 102 | : SkBitmapFilter(width), alpha(a), expWidth(expf(-alpha * width * width)) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 103 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 104 | |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 105 | float evaluate(float x) const override { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 106 | return SkTMax(0.f, float(expf(-alpha*x*x) - expWidth)); |
| 107 | } |
| 108 | protected: |
| 109 | float alpha, expWidth; |
| 110 | }; |
| 111 | |
| 112 | class SkTriangleFilter: public SkBitmapFilter { |
| 113 | public: |
| 114 | SkTriangleFilter(float width=1) |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 115 | : SkBitmapFilter(width) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 116 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 117 | |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 118 | float evaluate(float x) const override { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 119 | return SkTMax(0.f, fWidth - fabsf(x)); |
| 120 | } |
| 121 | protected: |
| 122 | }; |
| 123 | |
| 124 | class SkBoxFilter: public SkBitmapFilter { |
| 125 | public: |
| 126 | SkBoxFilter(float width=0.5f) |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 127 | : SkBitmapFilter(width) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 128 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 129 | |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 130 | float evaluate(float x) const override { |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 131 | return (x >= -fWidth && x < fWidth) ? 1.0f : 0.0f; |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 132 | } |
| 133 | protected: |
| 134 | }; |
| 135 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 136 | class SkHammingFilter: public SkBitmapFilter { |
| 137 | public: |
| 138 | SkHammingFilter(float width=1.f) |
| 139 | : SkBitmapFilter(width) { |
| 140 | } |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 141 | float evaluate(float x) const override { |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 142 | if (x <= -fWidth || x >= fWidth) { |
| 143 | return 0.0f; // Outside of the window. |
| 144 | } |
| 145 | if (x > -FLT_EPSILON && x < FLT_EPSILON) { |
| 146 | return 1.0f; // Special case the sinc discontinuity at the origin. |
| 147 | } |
humper@google.com | 16acf75 | 2013-07-19 21:12:08 +0000 | [diff] [blame] | 148 | const float xpi = x * static_cast<float>(SK_ScalarPI); |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 149 | |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 150 | return ((sk_float_sin(xpi) / xpi) * // sinc(x) |
| 151 | (0.54f + 0.46f * sk_float_cos(xpi / fWidth))); // hamming(x) |
| 152 | } |
| 153 | }; |
| 154 | |
| 155 | class SkLanczosFilter: public SkBitmapFilter { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 156 | public: |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 157 | SkLanczosFilter(float width=3.f) |
| 158 | : SkBitmapFilter(width) { |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 159 | } |
skia.committer@gmail.com | 9e1ec1a | 2013-07-10 07:00:58 +0000 | [diff] [blame] | 160 | |
mtklein | 36352bf | 2015-03-25 18:17:31 -0700 | [diff] [blame] | 161 | float evaluate(float x) const override { |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 162 | if (x <= -fWidth || x >= fWidth) { |
| 163 | return 0.0f; // Outside of the window. |
| 164 | } |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 165 | if (x > -FLT_EPSILON && x < FLT_EPSILON) { |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 166 | return 1.0f; // Special case the discontinuity at the origin. |
| 167 | } |
humper@google.com | 16acf75 | 2013-07-19 21:12:08 +0000 | [diff] [blame] | 168 | float xpi = x * static_cast<float>(SK_ScalarPI); |
humper@google.com | 138ebc3 | 2013-07-19 20:20:04 +0000 | [diff] [blame] | 169 | return (sk_float_sin(xpi) / xpi) * // sinc(x) |
| 170 | sk_float_sin(xpi / fWidth) / (xpi / fWidth); // sinc(x/fWidth) |
skia.committer@gmail.com | 1f3c738 | 2013-07-20 07:00:58 +0000 | [diff] [blame] | 171 | } |
humper@google.com | b088947 | 2013-07-09 21:37:14 +0000 | [diff] [blame] | 172 | }; |
| 173 | |
| 174 | |
| 175 | #endif |