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Unified Diff: src/pdf/SkPDFShader.cpp

Issue 26389006: PDF: support perspective in simple shaders. (this version does not work well with tilling) (Closed) Base URL: https://skia.googlecode.com/svn/trunk
Patch Set: previous upload failed Created 7 years, 2 months ago
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Index: src/pdf/SkPDFShader.cpp
diff --git a/src/pdf/SkPDFShader.cpp b/src/pdf/SkPDFShader.cpp
index 70fb616a24f672cbf0b57603cf400defb69d0973..3f1b3c802a95a6cfbb742340f5b671a36a547851 100644
--- a/src/pdf/SkPDFShader.cpp
+++ b/src/pdf/SkPDFShader.cpp
@@ -210,16 +210,74 @@ static void tileModeCode(SkShader::TileMode mode, SkString* result) {
}
}
-static SkString linearCode(const SkShader::GradientInfo& info) {
- SkString function("{pop\n"); // Just ditch the y value.
+/**
+ * Returns PS function code that would apply perspective to a x, y point.
vandebo (ex-Chrome) 2013/10/21 19:23:19 nit: would apply -> applies
edisonn 2013/10/23 19:45:18 Done.
+ * The function assumes that the stack has at least two elements,
+ * and that the top 2 elements are numeric values.
+ * After ececuting this code on a PS stack, the last 2 elements are updated
vandebo (ex-Chrome) 2013/10/21 19:23:19 nit: ececuting -> executing
edisonn 2013/10/23 19:45:18 Done.
+ * while the rest of the stack is preserved intact.
+ * xy2xy is the inverse perspective matrix.
vandebo (ex-Chrome) 2013/10/21 19:23:19 nit: update or remove
edisonn 2013/10/23 19:45:18 Done.
+ */
+static SkString apply_perspective_to_coordinates(
+ const SkMatrix& inversePerspectiveMatrix) {
+ SkString code;
+ if (!inversePerspectiveMatrix.hasPerspective()) {
+ return code;
+ }
+
+ // Perspective matrix should be:
+ // 1 0 0
+ // 0 1 0
+ // p0 p1 p2
+
+ SkScalar p0 = inversePerspectiveMatrix[SkMatrix::kMPersp0];
+ SkScalar p1 = inversePerspectiveMatrix[SkMatrix::kMPersp1];
+ SkScalar p2 = inversePerspectiveMatrix[SkMatrix::kMPersp2];
+
+ // y = y / (p2 + p0 x + p1 y)
+ // x = x / (p2 + p0 x + p1 y)
+
+ // Input on stack: x y
+ code.append("dup "); // x y y
+ code.appendScalar(p1); // x y y p1
+ code.append(" mul " // x y y*p1
+ " 2 index "); // x y y*p1 x
+ code.appendScalar(p0); // x y y p1 x p0
+ code.append(" mul "); // x y y*p1 x*p0
+ code.appendScalar(p2); // x y y p1 x*p0 p2
+ code.append("add " // x y y*p1 x*p0+p2
+ "add " // x y y*p1+x*p0+p2
+ "1 index " // x y y*p1+x*p0+p2 y
+ "1 index " // x y y*p1+x*p0+p2 y y*p1+x*p0+p2
+ "div " // x y y*p1+x*p0+p2 y/(y*p1+x*p0+p2)
+ "4 1 roll " // y/(y*p1+x*p0+p2) x y y*p1+x*p0+p2
+ "exch " // y/(y*p1+x*p0+p2) x y*p1+x*p0+p2 y
+ "pop " // y/(y*p1+x*p0+p2) x y*p1+x*p0+p2
+ "div " // y/(y*p1+x*p0+p2) x/(y*p1+x*p0+p2)
+ "exch\n"); // x/(y*p1+x*p0+p2) y/(y*p1+x*p0+p2)
+
+ return code;
+}
+
+static SkString linearCode(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) {
+ SkString function("{");
+
+ function.append(apply_perspective_to_coordinates(perspectiveRemover));
+
+ function.append("pop\n"); // Just ditch the y value.
tileModeCode(info.fTileMode, &function);
gradientFunctionCode(info, &function);
function.append("}");
return function;
}
-static SkString radialCode(const SkShader::GradientInfo& info) {
+static SkString radialCode(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) {
SkString function("{");
+
+ function.append(apply_perspective_to_coordinates(perspectiveRemover));
+
// Find the distance from the origin.
function.append("dup " // x y y
"mul " // x y^2
@@ -239,7 +297,8 @@ static SkString radialCode(const SkShader::GradientInfo& info) {
with one simplification, the coordinate space has been scaled so that
Dr = 1. This means we don't need to scale the entire equation by 1/Dr^2.
*/
-static SkString twoPointRadialCode(const SkShader::GradientInfo& info) {
+static SkString twoPointRadialCode(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) {
SkScalar dx = info.fPoint[0].fX - info.fPoint[1].fX;
SkScalar dy = info.fPoint[0].fY - info.fPoint[1].fY;
SkScalar sr = info.fRadius[0];
@@ -249,6 +308,9 @@ static SkString twoPointRadialCode(const SkShader::GradientInfo& info) {
// We start with a stack of (x y), copy it and then consume one copy in
// order to calculate b and the other to calculate c.
SkString function("{");
+
+ function.append(apply_perspective_to_coordinates(perspectiveRemover));
+
function.append("2 copy ");
// Calculate -b and b^2.
@@ -286,7 +348,8 @@ static SkString twoPointRadialCode(const SkShader::GradientInfo& info) {
/* Conical gradient shader, based on the Canvas spec for radial gradients
See: http://www.w3.org/TR/2dcontext/#dom-context-2d-createradialgradient
*/
-static SkString twoPointConicalCode(const SkShader::GradientInfo& info) {
+static SkString twoPointConicalCode(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) {
SkScalar dx = info.fPoint[1].fX - info.fPoint[0].fX;
SkScalar dy = info.fPoint[1].fY - info.fPoint[0].fY;
SkScalar r0 = info.fRadius[0];
@@ -300,6 +363,9 @@ static SkString twoPointConicalCode(const SkShader::GradientInfo& info) {
// We start with a stack of (x y), copy it and then consume one copy in
// order to calculate b and the other to calculate c.
SkString function("{");
+
+ function.append(apply_perspective_to_coordinates(perspectiveRemover));
+
function.append("2 copy ");
// Calculate b and b^2; b = -2 * (y * dy + x * dx + r0 * dr).
@@ -395,7 +461,8 @@ static SkString twoPointConicalCode(const SkShader::GradientInfo& info) {
return function;
}
-static SkString sweepCode(const SkShader::GradientInfo& info) {
+static SkString sweepCode(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) {
SkString function("{exch atan 360 div\n");
tileModeCode(info.fTileMode, &function);
gradientFunctionCode(info, &function);
@@ -725,10 +792,49 @@ SkPDFAlphaFunctionShader::SkPDFAlphaFunctionShader(SkPDFShader::State* state)
SkMatrix::I());
}
+// Finds affine and persp such that in = affine * persp.
+// but it returns the inverse of perspective matrix.
+static bool split_perspective(const SkMatrix in, SkMatrix* affine,
+ SkMatrix* perspectiveInverse) {
+ const SkScalar p2 = in[SkMatrix::kMPersp2];
+
+ if (SkScalarNearlyZero(p2)) {
+ return false;
+ }
+
+ const SkScalar zero = SkIntToScalar(0);
+ const SkScalar one = SkIntToScalar(1);
+
+ const SkScalar sx = in[SkMatrix::kMScaleX];
+ const SkScalar kx = in[SkMatrix::kMSkewX];
+ const SkScalar tx = in[SkMatrix::kMTransX];
+ const SkScalar ky = in[SkMatrix::kMSkewY];
+ const SkScalar sy = in[SkMatrix::kMScaleY];
+ const SkScalar ty = in[SkMatrix::kMTransY];
+ const SkScalar p0 = in[SkMatrix::kMPersp0];
+ const SkScalar p1 = in[SkMatrix::kMPersp1];
+
+ // Perspective matrix would be:
+ // 1 0 0
+ // 0 1 0
+ // p0 p1 p2
+ // But we need the inverse of persp.
+ perspectiveInverse->setAll(one, zero, zero,
+ zero, one, zero,
+ -p0 / p2, -p1/p2, 1/p2);
+
+ affine->setAll(sx - p0 * tx / p2, kx - p1 * tx / p2, tx / p2,
+ ky - p0 * ty / p2, sy - p1 * ty / p2, ty / p2,
+ zero, zero, one);
+
+ return true;
+}
+
SkPDFFunctionShader::SkPDFFunctionShader(SkPDFShader::State* state)
: SkPDFDict("Pattern"),
fState(state) {
- SkString (*codeFunction)(const SkShader::GradientInfo& info) = NULL;
+ SkString (*codeFunction)(const SkShader::GradientInfo& info,
+ const SkMatrix& perspectiveRemover) = NULL;
SkPoint transformPoints[2];
// Depending on the type of the gradient, we want to transform the
@@ -780,8 +886,24 @@ SkPDFFunctionShader::SkPDFFunctionShader(SkPDFShader::State* state)
// the gradient can be drawn on on the unit segment.
SkMatrix mapperMatrix;
unitToPointsMatrix(transformPoints, &mapperMatrix);
+
+ SkMatrix perspectiveInverseOnly = SkMatrix::I();
+
SkMatrix finalMatrix = fState.get()->fCanvasTransform;
finalMatrix.preConcat(fState.get()->fShaderTransform);
+
+ // Preserves as much as posible in the final matrix, and only removes
+ // the perspective. The inverse of the perspective is stored in
+ // perspectiveInverseOnly matrix and has 3 useful numbers
+ // (p0, p1, p2), while everything else is either 0 or 1.
+ // In this way the shader will handle it eficiently, with minimal code.
+ if (finalMatrix.hasPerspective()) {
+ if (!split_perspective(finalMatrix,
+ &finalMatrix, &perspectiveInverseOnly)) {
+ return;
+ }
+ }
+
finalMatrix.preConcat(mapperMatrix);
SkRect bbox;
@@ -812,9 +934,9 @@ SkPDFFunctionShader::SkPDFFunctionShader(SkPDFShader::State* state)
inverseMapperMatrix.mapRadius(info->fRadius[0]);
twoPointRadialInfo.fRadius[1] =
inverseMapperMatrix.mapRadius(info->fRadius[1]);
- functionCode = codeFunction(twoPointRadialInfo);
+ functionCode = codeFunction(twoPointRadialInfo, perspectiveInverseOnly);
} else {
- functionCode = codeFunction(*info);
+ functionCode = codeFunction(*info, perspectiveInverseOnly);
}
SkAutoTUnref<SkPDFDict> pdfShader(new SkPDFDict);
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