61 lines
2.2 KiB
C++
61 lines
2.2 KiB
C++
#include "SkMatrix.h"
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static void computeOuterProduct(SkScalar op[4],
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const SkPoint pts0[3], const SkPoint& ave0,
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const SkPoint pts1[3], const SkPoint& ave1) {
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bzero(op, 4 * sizeof(op[0]));
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for (int i = 0; i < 3; i++) {
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SkScalar x0 = pts0[i].fX - ave0.fX;
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SkScalar y0 = pts0[i].fY - ave0.fY;
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SkScalar x1 = pts1[i].fX - ave1.fX;
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SkScalar y1 = pts1[i].fY - ave1.fY;
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op[0] += SkScalarMul(x0, x1);
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op[1] += SkScalarMul(x0, y1);
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op[2] += SkScalarMul(y0, x1);
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op[3] += SkScalarMul(y0, y1);
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}
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}
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static SkScalar dot(SkScalar ax, SkScalar ay, SkScalar bx, SkScalar by) {
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return SkScalarMul(ax, bx) + SkScalarMul(ay, by);
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}
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bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]) {
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const SkPoint& srcAve = src[0];
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const SkPoint& dstAve = dst[0];
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SkScalar srcOP[4], dstOP[4];
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computeOuterProduct(srcOP, src, srcAve, src, srcAve);
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computeOuterProduct(dstOP, src, srcAve, dst, dstAve);
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SkScalar det = SkScalarMul(srcOP[0], srcOP[3]) - SkScalarMul(srcOP[1], srcOP[2]);
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// need SkScalarNearlyZeroSquared for this (to match Chrome's fix)
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if (SkScalarNearlyZero(det)) {
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return false;
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}
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SkScalar invDet = SkScalarInvert(det);
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// now compute invDet * [srcOP]T * [dstOP]
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// scale and transpose
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const SkScalar srcOP0 = SkScalarMul( srcOP[3], invDet);
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const SkScalar srcOP1 = SkScalarMul(-srcOP[1], invDet);
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const SkScalar srcOP2 = SkScalarMul(-srcOP[2], invDet);
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const SkScalar srcOP3 = SkScalarMul( srcOP[0], invDet);
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matrix->reset();
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matrix->setScaleX(dot(srcOP0, srcOP1, dstOP[0], dstOP[2]));
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matrix->setSkewX( dot(srcOP2, srcOP3, dstOP[0], dstOP[2]));
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matrix->setSkewY (dot(srcOP0, srcOP1, dstOP[1], dstOP[3]));
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matrix->setScaleY(dot(srcOP2, srcOP3, dstOP[1], dstOP[3]));
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matrix->setTranslateX(dstAve.fX - dot(srcAve.fX, srcAve.fY,
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matrix->getScaleX(), matrix->getSkewX()));
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matrix->setTranslateY(dstAve.fY - dot(srcAve.fX, srcAve.fY,
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matrix->getSkewY(), matrix->getScaleY()));
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return true;
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}
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