ddab2276cb
of points in a quadratic curve is within +/- 2x the value determined by the previous expensive method. Running a similar approximation method on the Guimark2 HTML5 Charting demo drops the share of time spent in SkPoint::distanceToLineSegmentBetweenSqd() from 4.57% to under 0.6%, although SkPath::Iter::next(), SkPath::lineTo(), and GrPathUtils::quadraticPointCount() all increase a bit. Using a similar approximation method for SampleSlides.cpp produces visually reasonable results. Without a relevant gm (it looks like gm/pathfill.cpp doesn't have explicit quadratics?) I'm not sure how to get a better output quality test. We could avoid code duplication by: - have two implementations in GrPathUtils (computedQuadraticPointCount() & estimatedQuadraticPointCount() are my working titles) - use a #define to select between them at compile time - expose both of them in the header file for this test to access git-svn-id: http://skia.googlecode.com/svn/trunk@1540 2bbb7eff-a529-9590-31e7-b0007b416f81
130 lines
4.1 KiB
C++
130 lines
4.1 KiB
C++
#include "SkPoint.h"
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#include "SkScalar.h"
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#include "Test.h"
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/*
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Duplicates lots of code from gpu/src/GrPathUtils.cpp
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It'd be nice not to do so, but that code's set up currently to only have a single implementation.
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*/
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#define MAX_COEFF_SHIFT 6
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static const uint32_t MAX_POINTS_PER_CURVE = 1 << MAX_COEFF_SHIFT;
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static inline int cheap_distance(SkScalar dx, SkScalar dy) {
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int idx = SkAbs32(SkScalarRound(dx));
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int idy = SkAbs32(SkScalarRound(dy));
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if (idx > idy) {
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idx += idy >> 1;
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} else {
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idx = idy + (idx >> 1);
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}
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return idx;
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}
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static inline int diff_to_shift(SkScalar dx, SkScalar dy) {
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int dist = cheap_distance(dx, dy);
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return (32 - SkCLZ(dist));
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}
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uint32_t estimatedQuadraticPointCount(const SkPoint points[], SkScalar tol) {
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int shift = diff_to_shift(points[1].fX * 2 - points[2].fX - points[0].fX,
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points[1].fY * 2 - points[2].fY - points[0].fY);
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SkASSERT(shift >= 0);
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//SkDebugf("Quad shift %d;", shift);
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// bias to more closely approximate exact value, then clamp to zero
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shift -= 2;
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shift &= ~(shift>>31);
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if (shift > MAX_COEFF_SHIFT) {
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shift = MAX_COEFF_SHIFT;
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}
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uint32_t count = 1 << shift;
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//SkDebugf(" biased shift %d, scale %u\n", shift, count);
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return count;
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}
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uint32_t computedQuadraticPointCount(const SkPoint points[], SkScalar tol) {
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SkScalar d = points[1].distanceToLineSegmentBetween(points[0], points[2]);
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if (d < tol) {
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return 1;
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} else {
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int temp = SkScalarCeil(SkScalarSqrt(SkScalarDiv(d, tol)));
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uint32_t count = SkMinScalar(SkNextPow2(temp), MAX_POINTS_PER_CURVE);
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return count;
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}
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}
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// Curve from samplecode/SampleSlides.cpp
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static const int gXY[] = {
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4, 0, 0, -4, 8, -4, 12, 0, 8, 4, 0, 4
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};
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static const int gSawtooth[] = {
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0, 0, 10, 10, 20, 20, 30, 10, 40, 0, 50, -10, 60, -20, 70, -10, 80, 0
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};
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static const int gOvalish[] = {
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0, 0, 5, 15, 20, 20, 35, 15, 40, 0
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};
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static const int gSharpSawtooth[] = {
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0, 0, 1, 10, 2, 0, 3, -10, 4, 0
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};
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// Curve crosses back over itself around 0,10
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static const int gRibbon[] = {
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-4, 0, 4, 20, 0, 25, -4, 20, 4, 0
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};
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static bool one_d_pe(const int* array, const unsigned int count,
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skiatest::Reporter* reporter) {
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SkPoint path [3];
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path[1] = SkPoint::Make(SkIntToScalar(array[0]), SkIntToScalar(array[1]));
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path[2] = SkPoint::Make(SkIntToScalar(array[2]), SkIntToScalar(array[3]));
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int numErrors = 0;
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for (unsigned i = 4; i < (count); i += 2) {
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path[0] = path[1];
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path[1] = path[2];
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path[2] = SkPoint::Make(SkIntToScalar(array[i]),
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SkIntToScalar(array[i+1]));
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uint32_t computedCount =
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computedQuadraticPointCount(path, SkIntToScalar(1));
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uint32_t estimatedCount =
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estimatedQuadraticPointCount(path, SkIntToScalar(1));
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// Allow estimated to be off by a factor of two, but no more.
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if ((estimatedCount > 2 * computedCount) ||
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(computedCount > estimatedCount * 2)) {
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SkString errorDescription;
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errorDescription.printf(
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"Curve from %.2f %.2f through %.2f %.2f to %.2f %.2f "
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"computes %d, estimates %d\n",
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path[0].fX, path[0].fY, path[1].fX, path[1].fY,
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path[2].fX, path[2].fY, computedCount, estimatedCount);
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numErrors++;
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reporter->reportFailed(errorDescription);
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}
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}
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if (numErrors > 0)
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printf("%d curve segments differ\n", numErrors);
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return (numErrors == 0);
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}
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static void TestQuadPointCount(skiatest::Reporter* reporter) {
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one_d_pe(gXY, SK_ARRAY_COUNT(gXY), reporter);
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one_d_pe(gSawtooth, SK_ARRAY_COUNT(gSawtooth), reporter);
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one_d_pe(gOvalish, SK_ARRAY_COUNT(gOvalish), reporter);
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one_d_pe(gSharpSawtooth, SK_ARRAY_COUNT(gSharpSawtooth), reporter);
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one_d_pe(gRibbon, SK_ARRAY_COUNT(gRibbon), reporter);
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}
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static void TestPathCoverage(skiatest::Reporter* reporter) {
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TestQuadPointCount(reporter);
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}
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#include "TestClassDef.h"
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DEFINE_TESTCLASS("PathCoverage", PathCoverageTestClass, TestPathCoverage)
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