Add ability to extract YUV planes from SkImage

src/image/SkImage.cpp

Index: src/image/SkImage.cpp
diff --git a/src/image/SkImage.cpp b/src/image/SkImage.cpp
index 25370bcff15e09ad2e7276ec3a98f23e4a79cf35..f6033a2b06b161aebc3931c1d1746fb322bf6173 100644
--- a/src/image/SkImage.cpp
+++ b/src/image/SkImage.cpp
@@ -258,6 +258,83 @@ bool SkImage::readPixels(const SkPixmap& pmap, int srcX, int srcY, CachingHint c
     return this->readPixels(pmap.info(), pmap.writable_addr(), pmap.rowBytes(), srcX, srcY, chint);
 }
 
+#if SK_SUPPORT_GPU
+#include "GrTextureToYUVPlanes.h"
+#endif
+
+#define HACKY_RASTER_IMPL 1
+
+#if HACKY_RASTER_IMPL
+ // Shouldn't really include from effects here.
+#include "../effects/SkColorMatrixFilter.h"
+
+static const float kYUVColorSpaceInvMatrices[][20] = {
+    {0.299001f,  0.586998f,  0.114001f,  0.f, 0.0000821798f * 255.f,
+    -0.168736f, -0.331263f,  0.499999f,  0.f, 0.499954f     * 255.f,
+     0.499999f, -0.418686f, -0.0813131f, 0.f, 0.499941f     * 255.f,
+     0.f,        0.f,        0.f,        1.f, 0.f           * 255.f},
+
+    {0.256951f,  0.504421f,  0.0977346f, 0.f, 0.0625f * 255.f,

[reed1, 2016/01/28 22:12:45]

// I'm this colorspace

+    -0.148212f, -0.290954f,  0.439166f,  0.f, 0.5f    * 255.f,
+     0.439166f, -0.367886f, -0.0712802f, 0.f, 0.5f    * 255.f,
+     0.f,        0.f,        0.f,        1.f, 0.f     * 255.f},
+
+    {0.182663f,  0.614473f, 0.061971f, 0.f, 0.0625f * 255.f,
+    -0.100672f, -0.338658f, 0.43933f,  0.f, 0.5f    * 255.f,
+     0.439142f, -0.39891f, -0.040231f, 0.f, 0.5f    * 255.f,
+     0.f,        0.f,       0.f,       1.f, 0.f     * 255.f},
+};
+#endif
+
+bool SkImage::asYUV8Planes(const SkISize sizes[3], void* const planes[3], const size_t rowBytes[3],
+                           SkYUVColorSpace colorSpace) {
+#if SK_SUPPORT_GPU
+    if (GrTexture* texture = as_IB(this)->peekTexture()) {
+        if (GrTextureToYUVPlanes(texture, sizes, planes, rowBytes, colorSpace)) {
+            return true;
+        }
+    }
+#endif
+#if !HACKY_RASTER_IMPL
+    return false;
+#else  // This seems to work for Y but not U and V
+    SkPixmap pixmap;
+    SkAutoTDeleteArray<uint32_t> pixels(0);
+    if (!this->peekPixels(&pixmap)) {
+        // Should this be premul?
+        SkImageInfo info = SkImageInfo::MakeN32Premul(this->width(), this->height());
+        pixels.reset(new uint32_t[this->width() * this->height()]);
+        pixmap.reset(info, pixels.get(), 0);

[reed1, 2016/01/28 22:12:45]

pass the explicit rowBYtes (width() * 4)

+        if (!this->readPixels(pixmap, 0, 0, kDisallow_CachingHint)) {
+            return false;
+      }
+    }
+    for (int i = 0; i < 3; ++i) {
+        size_t rb = rowBytes[i] ? rowBytes[i] : sizes[i].fWidth;
+        SkAutoTUnref<SkSurface> surface(SkSurface::NewRasterDirect(
+                SkImageInfo::MakeA8(sizes[i].fWidth, sizes[i].fHeight), planes[i], rb));
+        SkPaint paint;
+        paint.setFilterQuality(kLow_SkFilterQuality);
+        paint.setXfermodeMode(SkXfermode::kSrc_Mode);
+        SkColorMatrix replicateChannel;
+        for (int j = 0; j < 20; ++j) {
+            replicateChannel.fMat[j] = 0.f;
+        }
+        replicateChannel.fMat[0+i] = 1.f;
+        replicateChannel.fMat[5+i] = 1.f;
+        replicateChannel.fMat[10+i] = 1.f;
+        replicateChannel.fMat[15+i] = 1.f;
+        SkColorMatrix::SetConcat(replicateChannel.fMat, replicateChannel.fMat,
+                                 kYUVColorSpaceInvMatrices[colorSpace]);
+        paint.setColorFilter(SkColorMatrixFilter::Create(replicateChannel))->unref();
+        surface->getCanvas()->drawImageRect(this, SkIRect::MakeWH(this->width(), this->height()),
+                                            SkRect::MakeIWH(surface->width(), surface->height()),
+                                            &paint);
+    }
+    return true;
+#endif
+}
+
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 SkImage* SkImage::NewFromBitmap(const SkBitmap& bm) {