Add ability to extract YUV planes from SkImage

gm/imagetoyuvplanes.cpp

Index: gm/imagetoyuvplanes.cpp
diff --git a/gm/imagetoyuvplanes.cpp b/gm/imagetoyuvplanes.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f0cf788d159cff8a6e07dd3787c7b3a0668e3fab
--- /dev/null
+++ b/gm/imagetoyuvplanes.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+
+#include <SkSurface.h>
+#include "gm.h"
+#include "SkBitmap.h"
+#include "SkGradientShader.h"
+#include "SkImage.h"
+
+static SkImage* create_image(GrContext* context, int width, int height) {
+    SkAutoTUnref<SkSurface> surface;
+    SkImageInfo info = SkImageInfo::MakeN32Premul(width, height);
+    if (context) {
+        surface.reset(SkSurface::NewRenderTarget(context,  SkSurface::kYes_Budgeted, info, 0));
+    } else {
+        surface.reset(SkSurface::NewRaster(info));
+    }
+    if (!surface) {
+        return nullptr;
+    }
+    // Create an RGB image from which we will extract planes
+    SkPaint paint;
+    static const SkColor kColors[] =
+            { SK_ColorBLUE, SK_ColorYELLOW, SK_ColorGREEN, SK_ColorWHITE };
+    SkScalar r = (width + height) / 4.f;
+    paint.setShader(SkGradientShader::CreateRadial(SkPoint::Make(0,0), r, kColors,
+                                                   nullptr, SK_ARRAY_COUNT(kColors),
+                                                   SkShader::kMirror_TileMode))->unref();
+
+    surface->getCanvas()->drawPaint(paint);
+    return surface->newImageSnapshot();
+}
+
+DEF_SIMPLE_GM(image_to_yuv_planes, canvas, 120, 525) {
+    static const SkScalar kPad = 5.f;
+    static const int kImageSize = 32;
+
+    GrContext *context = canvas->getGrContext();
+    SkAutoTUnref<SkImage> rgbImage(create_image(context, kImageSize, kImageSize));
+    if (!rgbImage) {
+        return;
+    }
+
+    canvas->drawImage(rgbImage, kPad, kPad);

[robertphillips, 2016/01/29 20:33:13]

// Test out 444, 422 and 42(1.333) YUV formats 

?

If that comment is correct why are we testing 42(1.333) and not 421 ?

[bsalomon, 2016/02/01 20:27:45]

I wasn't necessarily thinking about particular YUV formats, but wanted to
exercise three code paths - all planes the same size, uv the same size, and all
different. Added comment.

+    static const SkISize kSizes[][3] = {
+        {{kImageSize, kImageSize}, {kImageSize  , kImageSize  }, {kImageSize,   kImageSize  }},
+        {{kImageSize, kImageSize}, {kImageSize/2, kImageSize/2}, {kImageSize/2, kImageSize/2}},
+        {{kImageSize, kImageSize}, {kImageSize/2, kImageSize/2}, {kImageSize/3, kImageSize/3}}
+    };
+
+    SkScalar x = kPad;
+    for (size_t s = 0; s < SK_ARRAY_COUNT(kSizes); ++s) {
+        SkScalar y = rgbImage->height() + 2 * kPad;
+
+        const SkISize *sizes = kSizes[s];
+        SkAutoTDeleteArray<uint8_t> yPlane(new uint8_t[sizes[0].fWidth * sizes[0].fHeight]);
+        SkAutoTDeleteArray<uint8_t> uPlane(new uint8_t[sizes[1].fWidth * sizes[1].fHeight]);
+        SkAutoTDeleteArray<uint8_t> vPlane(new uint8_t[sizes[2].fWidth * sizes[2].fHeight]);
+
+        void *planes[3] = {yPlane.get(), uPlane.get(), vPlane.get()};

[robertphillips, 2016/01/29 20:33:13]

Should we exercise the rowBytes ?

[bsalomon, 2016/02/01 20:27:45]

Done.

+        size_t rowBytes[3] = {0, 0, 0};
+
+        // Convert the RGB image to YUV planes using each YUV color space and draw the YUV planes
+        // to the canvas.
+        SkBitmap yuvBmps[3];
+        yuvBmps[0].setInfo(SkImageInfo::MakeA8(sizes[0].fWidth, sizes[0].fHeight));
+        yuvBmps[1].setInfo(SkImageInfo::MakeA8(sizes[1].fWidth, sizes[1].fHeight));
+        yuvBmps[2].setInfo(SkImageInfo::MakeA8(sizes[2].fWidth, sizes[2].fHeight));
+        yuvBmps[0].setPixels(yPlane.get());
+        yuvBmps[1].setPixels(uPlane.get());
+        yuvBmps[2].setPixels(vPlane.get());
+
+        for (int space = kJPEG_SkYUVColorSpace; space <= kLastEnum_SkYUVColorSpace; ++space) {
+            // Clear the planes so we don't accidentally see the old values if there is a bug in
+            // readYUV8Planes().
+            memset(yPlane.get(), 0, sizes[0].fWidth * sizes[0].fHeight);
+            memset(uPlane.get(), 0, sizes[1].fWidth * sizes[1].fHeight);
+            memset(vPlane.get(), 0, sizes[2].fWidth * sizes[2].fHeight);
+            if (rgbImage->readYUV8Planes(sizes, planes, rowBytes,
+                                         static_cast<SkYUVColorSpace>(space))) {
+                yuvBmps[0].notifyPixelsChanged();
+                yuvBmps[1].notifyPixelsChanged();
+                yuvBmps[2].notifyPixelsChanged();
+                for (int i = 0; i < 3; ++i) {
+                    canvas->drawBitmap(yuvBmps[i], x, y);
+                    y += kPad + yuvBmps[i].height();
+                }
+            }
+        }
+
+        x += rgbImage->width() + kPad;
+    }
+}