commit 8294015fc83f51232c92722fccb86e8623b21f49
author Ethan Nicholas <ethannicholas@google.com> Thu Jan 10 13:58:14 2019 -0500
committer Skia Commit-Bot <skia-commit-bot@chromium.org> Fri Jan 11 14:23:06 2019 +0000
tree 24b67a16e0eec9e17e3fd1a10af588c8931bdf31
parent cb42fc0dc56fd7fd7e0f9584b49f7f1870e0275b

Fixed GPU perlin noise shaders under rotation.

Note that this does not fix perspective rendering, which it
turns out is broken under CPU also... so at least the behavior
is consistent between the two now.

Bug: skia:8250
Change-Id: I35187c9a9bcf403f61348a33ef1623afeec2e73e
Reviewed-on: https://skia-review.googlesource.com/c/182966
Reviewed-by: Brian Salomon <bsalomon@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>

src/shaders/SkPerlinNoiseShader.cpp

diff --git a/src/shaders/SkPerlinNoiseShader.cpp b/src/shaders/SkPerlinNoiseShader.cpp
index b0d464b..6e90011a 100644
--- a/src/shaders/SkPerlinNoiseShader.cpp
+++ b/src/shaders/SkPerlinNoiseShader.cpp
@@ -98,14 +98,15 @@
                      SkScalar baseFrequencyX, SkScalar baseFrequencyY,
                      const SkMatrix& matrix)
         {
-            SkVector vec[2] = {
-                { SkScalarInvert(baseFrequencyX),   SkScalarInvert(baseFrequencyY)  },
-                { SkIntToScalar(tileSize.fWidth),   SkIntToScalar(tileSize.fHeight) },
-            };
-            matrix.mapVectors(vec, 2);
+            SkVector tileVec;
+            matrix.mapVector(SkIntToScalar(tileSize.fWidth), SkIntToScalar(tileSize.fHeight),
+                             &tileVec);
 
-            fBaseFrequency.set(SkScalarInvert(vec[0].fX), SkScalarInvert(vec[0].fY));
-            fTileSize.set(SkScalarRoundToInt(vec[1].fX), SkScalarRoundToInt(vec[1].fY));
+            SkSize scale;
+            matrix.decomposeScale(&scale, nullptr);
+            fBaseFrequency.set(baseFrequencyX * SkScalarInvert(scale.width()),
+                               baseFrequencyY * SkScalarInvert(scale.height()));
+            fTileSize.set(SkScalarRoundToInt(tileVec.fX), SkScalarRoundToInt(tileVec.fY));
             this->init(seed);
             if (!fTileSize.isEmpty()) {
                 this->stitch();
@@ -1404,7 +1405,7 @@
     SkASSERT(args.fContext);
 
     const auto localMatrix = this->totalLocalMatrix(args.fPreLocalMatrix, args.fPostLocalMatrix);
-    const auto matrix = SkMatrix::Concat(*args.fViewMatrix, *localMatrix);
+    const auto paintMatrix = SkMatrix::Concat(*args.fViewMatrix, *localMatrix);
 
     // Either we don't stitch tiles, either we have a valid tile size
     SkASSERT(!fStitchTiles || !fTileSize.isEmpty());
@@ -1414,7 +1415,7 @@
                                                                   fSeed,
                                                                   fBaseFrequencyX,
                                                                   fBaseFrequencyY,
-                                                                  matrix);
+                                                                  paintMatrix);
 
     SkMatrix m = *args.fViewMatrix;
     m.setTranslateX(-localMatrix->getTranslateX() + SK_Scalar1);