Add ability to extract YUV planes from SkImage

src/core/SkColorMatrixFilterRowMajor255.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkColorMatrixFilterRowMajor255.h"
 #include "SkColorPriv.h"
 #include "SkNx.h"
@@ skipping 14 matching lines @@
     const float* srcA = src + 15;
 
     for (int i = 0; i < 20; i += 4) {
         dst[i + SK_PMORDER_INDEX_A] = *srcA++;
         dst[i + SK_PMORDER_INDEX_R] = *srcR++;
         dst[i + SK_PMORDER_INDEX_G] = *srcG++;
         dst[i + SK_PMORDER_INDEX_B] = *srcB++;
     }
 }
 
-// src is [20] but some compilers won't accept __restrict__ on anything
-// but an raw pointer or reference
-void SkColorMatrixFilterRowMajor255::initState(const SkScalar* SK_RESTRICT src) {
-    transpose_to_pmorder(fTranspose, src);
+void SkColorMatrixFilterRowMajor255::initState() {
+    transpose_to_pmorder(fTranspose, fMatrix);
 
     const float* array = fMatrix;
 
     // check if we have to munge Alpha
     bool changesAlpha = (array[15] || array[16] || array[17] || (array[18] - 1) || array[19]);
     bool usesAlpha = (array[3] || array[8] || array[13]);
 
     if (changesAlpha || usesAlpha) {
         fFlags = changesAlpha ? 0 : kAlphaUnchanged_Flag;
     } else {
         fFlags = kAlphaUnchanged_Flag;
     }
     fFlags |= kSupports4f_Flag;
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkColorMatrixFilterRowMajor255::SkColorMatrixFilterRowMajor255(const SkScalar array[20]) {
     memcpy(fMatrix, array, 20 * sizeof(SkScalar));
-    this->initState(array);
+    this->initState();
 }
 
 uint32_t SkColorMatrixFilterRowMajor255::getFlags() const {
     return this->INHERITED::getFlags() | fFlags;
 }
 
 static Sk4f scale_rgb(float scale) {
     static_assert(SkPM4f::A == 3, "Alpha is lane 3");
     return Sk4f(scale, scale, scale, 1);
 }
@@ skipping 344 matching lines @@
     }
     str->append(")");
 }
 #endif
 
 ///////////////////////////////////////////////////////////////////////////////
 
 SkColorFilter* SkColorFilter::CreateMatrixFilterRowMajor255(const SkScalar array[20]) {
     return new SkColorMatrixFilterRowMajor255(array);
 }
+
+///////////////////////////////////////////////////////////////////////////////
+
+SkColorFilter* SkColorMatrixFilterRowMajor255::CreateSingleChannelOutput(const SkScalar row[5]) {
+    SkASSERT(row);
+    SkColorMatrixFilterRowMajor255* cf = new SkColorMatrixFilterRowMajor255();
+    static_assert(sizeof(SkScalar) * 5 * 4 == sizeof(cf->fMatrix), "sizes don't match");
+    for (int i = 0; i < 4; ++i) {
+        memcpy(cf->fMatrix + 5 * i, row, sizeof(SkScalar) * 5);
+    }
+    cf->initState();
+    return cf;
+}