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1 /* | 1 /* |
2 * Copyright 2014 Google Inc. | 2 * Copyright 2014 Google Inc. |
3 * | 3 * |
4 * Use of this source code is governed by a BSD-style license that can be | 4 * Use of this source code is governed by a BSD-style license that can be |
5 * found in the LICENSE file. | 5 * found in the LICENSE file. |
6 */ | 6 */ |
7 | 7 |
8 #include "SkDistanceFieldGen.h" | 8 #include "SkDistanceFieldGen.h" |
9 #include "SkPoint.h" | 9 #include "SkPoint.h" |
10 | 10 |
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100 } | 100 } |
101 data += 2*pad; | 101 data += 2*pad; |
102 edges += 2*pad; | 102 edges += 2*pad; |
103 } | 103 } |
104 } | 104 } |
105 | 105 |
106 // from Gustavson (2011) | 106 // from Gustavson (2011) |
107 // computes the distance to an edge given an edge normal vector and a pixel's al
pha value | 107 // computes the distance to an edge given an edge normal vector and a pixel's al
pha value |
108 // assumes that direction has been pre-normalized | 108 // assumes that direction has been pre-normalized |
109 static float edge_distance(const SkPoint& direction, float alpha) { | 109 static float edge_distance(const SkPoint& direction, float alpha) { |
110 #if 1 // formula (1) | |
111 return 0.5f - alpha; | |
112 #else // formula (4) | |
113 float dx = direction.fX; | 110 float dx = direction.fX; |
114 float dy = direction.fY; | 111 float dy = direction.fY; |
115 float distance; | 112 float distance; |
116 if (SkScalarNearlyZero(dx) || SkScalarNearlyZero(dy)) { | 113 if (SkScalarNearlyZero(dx) || SkScalarNearlyZero(dy)) { |
117 distance = 0.5f - alpha; | 114 distance = 0.5f - alpha; |
118 } else { | 115 } else { |
119 // this is easier if we treat the direction as being in the first octant | 116 // this is easier if we treat the direction as being in the first octant |
120 // (other octants are symmetrical) | 117 // (other octants are symmetrical) |
121 dx = SkScalarAbs(dx); | 118 dx = SkScalarAbs(dx); |
122 dy = SkScalarAbs(dy); | 119 dy = SkScalarAbs(dy); |
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139 } else if (alpha*dx < (dx - a1num)) { | 136 } else if (alpha*dx < (dx - a1num)) { |
140 distance = (0.5f - alpha)*dx; | 137 distance = (0.5f - alpha)*dx; |
141 // if 1 - a1 < alpha <= 1 | 138 // if 1 - a1 < alpha <= 1 |
142 } else { | 139 } else { |
143 // TODO: find a way to do this without square roots? | 140 // TODO: find a way to do this without square roots? |
144 distance = -0.5f*(dx + dy) + SkScalarSqrt(2.0f*dx*dy*(1.0f - alpha))
; | 141 distance = -0.5f*(dx + dy) + SkScalarSqrt(2.0f*dx*dy*(1.0f - alpha))
; |
145 } | 142 } |
146 } | 143 } |
147 | 144 |
148 return distance; | 145 return distance; |
149 #endif | |
150 } | 146 } |
151 | 147 |
152 static void init_distances(DFData* data, unsigned char* edges, int width, int he
ight) { | 148 static void init_distances(DFData* data, unsigned char* edges, int width, int he
ight) { |
153 // skip one pixel border | 149 // skip one pixel border |
154 DFData* currData = data; | 150 DFData* currData = data; |
155 DFData* prevData = data - width; | 151 DFData* prevData = data - width; |
156 DFData* nextData = data + width; | 152 DFData* nextData = data + width; |
157 | 153 |
158 for (int j = 0; j < height; ++j) { | 154 for (int j = 0; j < height; ++j) { |
159 for (int i = 0; i < width; ++i) { | 155 for (int i = 0; i < width; ++i) { |
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516 *currDestPtr++ = (mask & (1 << i)) ? 0xff : 0; | 512 *currDestPtr++ = (mask & (1 << i)) ? 0xff : 0; |
517 } | 513 } |
518 } | 514 } |
519 currSrcScanLine += rowBytes; | 515 currSrcScanLine += rowBytes; |
520 *currDestPtr++ = 0; | 516 *currDestPtr++ = 0; |
521 } | 517 } |
522 sk_bzero(currDestPtr, (width+2)*sizeof(char)); | 518 sk_bzero(currDestPtr, (width+2)*sizeof(char)); |
523 | 519 |
524 return generate_distance_field_from_image(distanceField, copyPtr, width, hei
ght); | 520 return generate_distance_field_from_image(distanceField, copyPtr, width, hei
ght); |
525 } | 521 } |
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