Add usage of SkYUVAIndex as pre-step to transfer to new YUVA API

The plan foward is to have a new API on SkImage to make from YUVA
textures which a combination of array of textures and array of
SkYUVAIndex struct indicating which texture and channel to read for
each plane. This is a pre-step to let the old API use these ideas.

Bug: skia: 7903
Change-Id: I6a696db31a574247eb2abff60f2186a74b640142
Reviewed-on: https://skia-review.googlesource.com/128601
Commit-Queue: Weiliang Chen <weiliangc@chromium.org>
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Greg Daniel <egdaniel@google.com>

1 files changed, 36 insertions, 0 deletions

diff --git a/include/core/SkImageInfo.h b/include/core/SkImageInfo.h
index eb96f19723..cb0e6dbbee 100644
--- a/include/core/SkImageInfo.h
+++ b/include/core/SkImageInfo.h
@@ -219,6 +219,42 @@ enum SkYUVColorSpace {
     kLastEnum_SkYUVColorSpace = kRec709_SkYUVColorSpace,
 };
 
+/** \enum SkImageInfo::SkImageSourceChannel
+    Describes different channels we could read from image source.
+*/
+enum SkImageSourceChannel {
+    /** Describes the red channel; */
+    kR_SkImageSourceChannel,
+
+    /** Describes the green channel; */
+    kG_SkImageSourceChannel,
+
+    /** Describes the blue channel; */
+    kB_SkImageSourceChannel,
+
+    /** Describes the alpha channel; */
+    kA_SkImageSourceChannel,
+
+    /** Describes the alpha channel; */
+    kLastEnum_SkImageSourceChannel = kA_SkImageSourceChannel,
+};
+
+/** \struct SkYUVAIndex
+    Describes from which image source and which channel to read each individual YUVA plane.
+
+    SkYUVAIndex contains a index for which image source to read from and a enum for which channel
+    to read from.
+*/
+struct SK_API SkYUVAIndex {
+    /** The index is a number between -1..3 which definies which image source to read from, where -1
+     * means the image source doesn't exist. The assumption is we will always have image sources for
+     * each of YUV planes, but optionally have image source for A plane. */
+    int fIndex;
+    /** The channel describes from which channel to read the info from. Currently we only deal with
+     * YUV and NV12 and channel info is ignored. */
+    SkImageSourceChannel fChannel;
+};
+
 /** \struct SkImageInfo
     Describes pixel dimensions and encoding. SkBitmap, SkImage, PixMap, and SkSurface
     can be created from SkImageInfo. SkImageInfo can be retrieved from SkBitmap and