b549cc38c8
Change-Id: I6b08a74234b99bac866bad71014b94f7ec2d4bc8 Reviewed-on: https://skia-review.googlesource.com/10188 Commit-Queue: Herb Derby <herb@google.com> Reviewed-by: Brian Salomon <bsalomon@google.com>
71 lines
2.3 KiB
C++
71 lines
2.3 KiB
C++
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/*
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* Copyright 2011 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "SkMatrix.h"
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#include "SkMalloc.h"
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// FIXME: needs to be in a header
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bool SkSetPoly3To3(SkMatrix* matrix, const SkPoint src[3], const SkPoint dst[3]);
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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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sk_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] += x0 * x1;
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op[1] += x0 * y1;
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op[2] += y0 * x1;
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op[3] += 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 ax * bx + 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 = srcOP[0] * srcOP[3] - 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 = srcOP[3] * invDet;
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const SkScalar srcOP1 = -srcOP[1] * invDet;
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const SkScalar srcOP2 = -srcOP[2] * invDet;
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const SkScalar srcOP3 = 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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