1 /*
2 * Copyright 2011 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 #include "SkMath.h"
9 #include "SkPoint.h"
10 #include "SkScalar.h"
11 #include "Test.h"
12
13 /*
14 Duplicates lots of code from gpu/src/GrPathUtils.cpp
15 It'd be nice not to do so, but that code's set up currently to only have
16 a single implementation.
17 */
18
19 // Sk uses 6, Gr (implicitly) used 10, both apparently arbitrarily.
20 #define MAX_COEFF_SHIFT 6
21 static const uint32_t MAX_POINTS_PER_CURVE = 1 << MAX_COEFF_SHIFT;
22
23 // max + 0.5 min has error [0.0, 0.12]
24 // max + 0.375 min has error [-.03, 0.07]
25 // 0.96043387 max + 0.397824735 min has error [-.06, +.05]
26 // For determining the maximum possible number of points to use in
27 // drawing a quadratic, we want to err on the high side.
cheap_distance(SkScalar dx,SkScalar dy)28 static inline int cheap_distance(SkScalar dx, SkScalar dy) {
29 int idx = SkAbs32(SkScalarRoundToInt(dx));
30 int idy = SkAbs32(SkScalarRoundToInt(dy));
31 if (idx > idy) {
32 idx += idy >> 1;
33 } else {
34 idx = idy + (idx >> 1);
35 }
36 return idx;
37 }
38
estimate_distance(const SkPoint points[])39 static inline int estimate_distance(const SkPoint points[]) {
40 return cheap_distance(points[1].fX * 2 - points[2].fX - points[0].fX,
41 points[1].fY * 2 - points[2].fY - points[0].fY);
42 }
43
compute_distance(const SkPoint points[])44 static inline SkScalar compute_distance(const SkPoint points[]) {
45 return points[1].distanceToLineSegmentBetween(points[0], points[2]);
46 }
47
estimate_pointCount(int distance)48 static inline uint32_t estimate_pointCount(int distance) {
49 // Includes -2 bias because this estimator runs 4x high?
50 int shift = 30 - SkCLZ(distance);
51 // Clamp to zero if above subtraction went negative.
52 shift &= ~(shift>>31);
53 if (shift > MAX_COEFF_SHIFT) {
54 shift = MAX_COEFF_SHIFT;
55 }
56 return 1 << shift;
57 }
58
compute_pointCount(SkScalar d,SkScalar tol)59 static inline uint32_t compute_pointCount(SkScalar d, SkScalar tol) {
60 if (d < tol) {
61 return 1;
62 } else {
63 int temp = SkScalarCeilToInt(SkScalarSqrt(d / tol));
64 uint32_t count = SkMin32(SkNextPow2(temp), MAX_POINTS_PER_CURVE);
65 return count;
66 }
67 }
68
quadraticPointCount_EE(const SkPoint points[])69 static uint32_t quadraticPointCount_EE(const SkPoint points[]) {
70 int distance = estimate_distance(points);
71 return estimate_pointCount(distance);
72 }
73
quadraticPointCount_EC(const SkPoint points[],SkScalar tol)74 static uint32_t quadraticPointCount_EC(const SkPoint points[], SkScalar tol) {
75 int distance = estimate_distance(points);
76 return compute_pointCount(SkIntToScalar(distance), tol);
77 }
78
quadraticPointCount_CE(const SkPoint points[])79 static uint32_t quadraticPointCount_CE(const SkPoint points[]) {
80 SkScalar distance = compute_distance(points);
81 return estimate_pointCount(SkScalarRoundToInt(distance));
82 }
83
quadraticPointCount_CC(const SkPoint points[],SkScalar tol)84 static uint32_t quadraticPointCount_CC(const SkPoint points[], SkScalar tol) {
85 SkScalar distance = compute_distance(points);
86 return compute_pointCount(distance, tol);
87 }
88
89 // Curve from samplecode/SampleSlides.cpp
90 static const int gXY[] = {
91 4, 0, 0, -4, 8, -4, 12, 0, 8, 4, 0, 4
92 };
93
94 static const int gSawtooth[] = {
95 0, 0, 10, 10, 20, 20, 30, 10, 40, 0, 50, -10, 60, -20, 70, -10, 80, 0
96 };
97
98 static const int gOvalish[] = {
99 0, 0, 5, 15, 20, 20, 35, 15, 40, 0
100 };
101
102 static const int gSharpSawtooth[] = {
103 0, 0, 1, 10, 2, 0, 3, -10, 4, 0
104 };
105
106 // Curve crosses back over itself around 0,10
107 static const int gRibbon[] = {
108 -4, 0, 4, 20, 0, 25, -4, 20, 4, 0
109 };
110
one_d_pe(const int * array,const unsigned int count,skiatest::Reporter * reporter)111 static bool one_d_pe(const int* array, const unsigned int count,
112 skiatest::Reporter* reporter) {
113 SkPoint path [3];
114 path[1] = SkPoint::Make(SkIntToScalar(array[0]), SkIntToScalar(array[1]));
115 path[2] = SkPoint::Make(SkIntToScalar(array[2]), SkIntToScalar(array[3]));
116 int numErrors = 0;
117 for (unsigned i = 4; i < count; i += 2) {
118 path[0] = path[1];
119 path[1] = path[2];
120 path[2] = SkPoint::Make(SkIntToScalar(array[i]),
121 SkIntToScalar(array[i+1]));
122 uint32_t computedCount =
123 quadraticPointCount_CC(path, SkIntToScalar(1));
124 uint32_t estimatedCount =
125 quadraticPointCount_EE(path);
126
127 if (false) { // avoid bit rot, suppress warning
128 computedCount =
129 quadraticPointCount_EC(path, SkIntToScalar(1));
130 estimatedCount =
131 quadraticPointCount_CE(path);
132 }
133 // Allow estimated to be high by a factor of two, but no less than
134 // the computed value.
135 bool isAccurate = (estimatedCount >= computedCount) &&
136 (estimatedCount <= 2 * computedCount);
137
138 if (!isAccurate) {
139 ERRORF(reporter, "Curve from %.2f %.2f through %.2f %.2f to "
140 "%.2f %.2f computes %d, estimates %d\n",
141 path[0].fX, path[0].fY, path[1].fX, path[1].fY,
142 path[2].fX, path[2].fY, computedCount, estimatedCount);
143 numErrors++;
144 }
145 }
146
147 return (numErrors == 0);
148 }
149
150
151
TestQuadPointCount(skiatest::Reporter * reporter)152 static void TestQuadPointCount(skiatest::Reporter* reporter) {
153 one_d_pe(gXY, SK_ARRAY_COUNT(gXY), reporter);
154 one_d_pe(gSawtooth, SK_ARRAY_COUNT(gSawtooth), reporter);
155 one_d_pe(gOvalish, SK_ARRAY_COUNT(gOvalish), reporter);
156 one_d_pe(gSharpSawtooth, SK_ARRAY_COUNT(gSharpSawtooth), reporter);
157 one_d_pe(gRibbon, SK_ARRAY_COUNT(gRibbon), reporter);
158 }
159
DEF_TEST(PathCoverage,reporter)160 DEF_TEST(PathCoverage, reporter) {
161 TestQuadPointCount(reporter);
162
163 }
164