reed@android.com | 8a1c16f | 2008-12-17 15:59:43 +0000 | [diff] [blame^] | 1 | /* libs/graphics/sgl/SkAlphaRuns.cpp |
| 2 | ** |
| 3 | ** Copyright 2006, The Android Open Source Project |
| 4 | ** |
| 5 | ** Licensed under the Apache License, Version 2.0 (the "License"); |
| 6 | ** you may not use this file except in compliance with the License. |
| 7 | ** You may obtain a copy of the License at |
| 8 | ** |
| 9 | ** http://www.apache.org/licenses/LICENSE-2.0 |
| 10 | ** |
| 11 | ** Unless required by applicable law or agreed to in writing, software |
| 12 | ** distributed under the License is distributed on an "AS IS" BASIS, |
| 13 | ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 14 | ** See the License for the specific language governing permissions and |
| 15 | ** limitations under the License. |
| 16 | */ |
| 17 | |
| 18 | #include "SkAntiRun.h" |
| 19 | |
| 20 | void SkAlphaRuns::reset(int width) |
| 21 | { |
| 22 | SkASSERT(width > 0); |
| 23 | |
| 24 | fRuns[0] = SkToS16(width); |
| 25 | fRuns[width] = 0; |
| 26 | fAlpha[0] = 0; |
| 27 | |
| 28 | SkDEBUGCODE(fWidth = width;) |
| 29 | SkDEBUGCODE(this->validate();) |
| 30 | } |
| 31 | |
| 32 | void SkAlphaRuns::Break(int16_t runs[], uint8_t alpha[], int x, int count) |
| 33 | { |
| 34 | SkASSERT(count > 0 && x >= 0); |
| 35 | |
| 36 | // SkAlphaRuns::BreakAt(runs, alpha, x); |
| 37 | // SkAlphaRuns::BreakAt(&runs[x], &alpha[x], count); |
| 38 | |
| 39 | int16_t* next_runs = runs + x; |
| 40 | uint8_t* next_alpha = alpha + x; |
| 41 | |
| 42 | while (x > 0) |
| 43 | { |
| 44 | int n = runs[0]; |
| 45 | SkASSERT(n > 0); |
| 46 | |
| 47 | if (x < n) |
| 48 | { |
| 49 | alpha[x] = alpha[0]; |
| 50 | runs[0] = SkToS16(x); |
| 51 | runs[x] = SkToS16(n - x); |
| 52 | break; |
| 53 | } |
| 54 | runs += n; |
| 55 | alpha += n; |
| 56 | x -= n; |
| 57 | } |
| 58 | |
| 59 | runs = next_runs; |
| 60 | alpha = next_alpha; |
| 61 | x = count; |
| 62 | |
| 63 | for (;;) |
| 64 | { |
| 65 | int n = runs[0]; |
| 66 | SkASSERT(n > 0); |
| 67 | |
| 68 | if (x < n) |
| 69 | { |
| 70 | alpha[x] = alpha[0]; |
| 71 | runs[0] = SkToS16(x); |
| 72 | runs[x] = SkToS16(n - x); |
| 73 | break; |
| 74 | } |
| 75 | x -= n; |
| 76 | if (x <= 0) |
| 77 | break; |
| 78 | |
| 79 | runs += n; |
| 80 | alpha += n; |
| 81 | } |
| 82 | } |
| 83 | |
| 84 | void SkAlphaRuns::add(int x, U8CPU startAlpha, int middleCount, U8CPU stopAlpha, U8CPU maxValue) |
| 85 | { |
| 86 | SkASSERT(middleCount >= 0); |
| 87 | SkASSERT(x >= 0 && x + (startAlpha != 0) + middleCount + (stopAlpha != 0) <= fWidth); |
| 88 | |
| 89 | int16_t* runs = fRuns; |
| 90 | uint8_t* alpha = fAlpha; |
| 91 | |
| 92 | if (startAlpha) |
| 93 | { |
| 94 | SkAlphaRuns::Break(runs, alpha, x, 1); |
| 95 | /* I should be able to just add alpha[x] + startAlpha. |
| 96 | However, if the trailing edge of the previous span and the leading |
| 97 | edge of the current span round to the same super-sampled x value, |
| 98 | I might overflow to 256 with this add, hence the funny subtract (crud). |
| 99 | */ |
| 100 | unsigned tmp = alpha[x] + startAlpha; |
| 101 | SkASSERT(tmp <= 256); |
| 102 | alpha[x] = SkToU8(tmp - (tmp >> 8)); // was (tmp >> 7), but that seems wrong if we're trying to catch 256 |
| 103 | |
| 104 | runs += x + 1; |
| 105 | alpha += x + 1; |
| 106 | x = 0; |
| 107 | SkDEBUGCODE(this->validate();) |
| 108 | } |
| 109 | if (middleCount) |
| 110 | { |
| 111 | SkAlphaRuns::Break(runs, alpha, x, middleCount); |
| 112 | alpha += x; |
| 113 | runs += x; |
| 114 | x = 0; |
| 115 | do { |
| 116 | alpha[0] = SkToU8(alpha[0] + maxValue); |
| 117 | int n = runs[0]; |
| 118 | SkASSERT(n <= middleCount); |
| 119 | alpha += n; |
| 120 | runs += n; |
| 121 | middleCount -= n; |
| 122 | } while (middleCount > 0); |
| 123 | SkDEBUGCODE(this->validate();) |
| 124 | } |
| 125 | if (stopAlpha) |
| 126 | { |
| 127 | SkAlphaRuns::Break(runs, alpha, x, 1); |
| 128 | alpha[x] = SkToU8(alpha[x] + stopAlpha); |
| 129 | SkDEBUGCODE(this->validate();) |
| 130 | } |
| 131 | } |
| 132 | |
| 133 | #ifdef SK_DEBUG |
| 134 | void SkAlphaRuns::assertValid(int y, int maxStep) const |
| 135 | { |
| 136 | int max = (y + 1) * maxStep - (y == maxStep - 1); |
| 137 | |
| 138 | const int16_t* runs = fRuns; |
| 139 | const uint8_t* alpha = fAlpha; |
| 140 | |
| 141 | while (*runs) |
| 142 | { |
| 143 | SkASSERT(*alpha <= max); |
| 144 | alpha += *runs; |
| 145 | runs += *runs; |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | void SkAlphaRuns::dump() const |
| 150 | { |
| 151 | const int16_t* runs = fRuns; |
| 152 | const uint8_t* alpha = fAlpha; |
| 153 | |
| 154 | SkDebugf("Runs"); |
| 155 | while (*runs) |
| 156 | { |
| 157 | int n = *runs; |
| 158 | |
| 159 | SkDebugf(" %02x", *alpha); |
| 160 | if (n > 1) |
| 161 | SkDebugf(",%d", n); |
| 162 | alpha += n; |
| 163 | runs += n; |
| 164 | } |
| 165 | SkDebugf("\n"); |
| 166 | } |
| 167 | |
| 168 | void SkAlphaRuns::validate() const |
| 169 | { |
| 170 | SkASSERT(fWidth > 0); |
| 171 | |
| 172 | int count = 0; |
| 173 | const int16_t* runs = fRuns; |
| 174 | |
| 175 | while (*runs) |
| 176 | { |
| 177 | SkASSERT(*runs > 0); |
| 178 | count += *runs; |
| 179 | SkASSERT(count <= fWidth); |
| 180 | runs += *runs; |
| 181 | } |
| 182 | SkASSERT(count == fWidth); |
| 183 | } |
| 184 | #endif |
| 185 | |