Add SkCodec methods for individual frames

Add a version of getFrameInfo that returns information about a single
frame, allowing a client to skip creating the entire vector.

Add getFrameCount, for determining the number of frames in the image.

Reimplement std::vector<FrameInfo> getFrameInfo with the new methods.

Updates to the test:
- getFrameInfo(size_t, FrameInfo*) fails before parsing
- Test both versions of getFrameInfo
- Recreate the codec between tests, to test parsing

Change-Id: I77c19087f2f8dcf2c536d80167b18ad1ca96ae94
Reviewed-on: https://skia-review.googlesource.com/13190
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Chris Blume <cblume@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

1 files changed, 28 insertions, 7 deletions

diff --git a/include/codec/SkCodec.h b/include/codec/SkCodec.h
index 6d4352214c..aadcb059fe 100644
--- a/include/codec/SkCodec.h
+++ b/include/codec/SkCodec.h
@@ -593,6 +593,15 @@ public:
      */
     int outputScanline(int inputScanline) const;
 
+    /**
+     *  Return the number of frames in the image.
+     *
+     *  May require reading through the stream.
+     */
+    size_t getFrameCount() {
+        return this->onGetFrameCount();
+    }
+
     // The required frame for an independent frame is marked as
     // kNone.
     static constexpr size_t kNone = static_cast<size_t>(-1);
@@ -628,7 +637,18 @@ public:
     };
 
     /**
-     *  Return info about the frames in the image.
+     *  Return info about a single frame.
+     *
+     *  Only supported by multi-frame images. Does not read through the stream,
+     *  so it should be called after getFrameCount() to parse any frames that
+     *  have not already been parsed.
+     */
+    bool getFrameInfo(size_t index, FrameInfo* info) const {
+        return this->onGetFrameInfo(index, info);
+    }
+
+    /**
+     *  Return info about all the frames in the image.
      *
      *  May require reading through the stream to determine info about the
      *  frames (including the count).
@@ -637,9 +657,7 @@ public:
      *
      *  For single-frame images, this will return an empty vector.
      */
-    std::vector<FrameInfo> getFrameInfo() {
-        return this->onGetFrameInfo();
-    }
+    std::vector<FrameInfo> getFrameInfo();
 
     static constexpr int kRepetitionCountInfinite = -1;
 
@@ -800,9 +818,12 @@ protected:
                               SkTransferFunctionBehavior premulBehavior);
     SkColorSpaceXform* colorXform() const { return fColorXform.get(); }
 
-    virtual std::vector<FrameInfo> onGetFrameInfo() {
-        // empty vector - this is not animated.
-        return std::vector<FrameInfo>{};
+    virtual size_t onGetFrameCount() {
+        return 1;
+    }
+
+    virtual bool onGetFrameInfo(size_t, FrameInfo*) const {
+        return false;
     }
 
     virtual int onGetRepetitionCount() {