Merge pull request #620 from kojilin/master

Let gif's first frame using last frame's dispose

Author: sjudd

third_party/gif_decoder/src/main/java/com/bumptech/glide/gifdecoder/GifDecoder.java

@@ -318,10 +318,12 @@ public synchronized Bitmap getNextFrame() {
     status = STATUS_OK;
 
     GifFrame currentFrame = header.frames.get(framePointer);
-    GifFrame previousFrame = null;
+    GifFrame previousFrame;
     int previousIndex = framePointer - 1;
     if (previousIndex >= 0) {
       previousFrame = header.frames.get(previousIndex);
+    } else {
+      previousFrame = header.frames.get(getFrameCount() - 1);
     }
 
     final int savedBgColor = header.bgColor;

third_party/gif_decoder/src/test/java/com/bumptech/glide/gifdecoder/GifDecoderTest.java

@@ -2,6 +2,8 @@
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
+import static org.junit.Assert.assertTrue;
+import static org.robolectric.Shadows.shadowOf;
 
 import android.graphics.Bitmap;
 import android.support.annotation.NonNull;
@@ -14,8 +16,12 @@
 import org.robolectric.RobolectricTestRunner;
 import org.robolectric.Shadows;
 import org.robolectric.annotation.Config;
+import org.robolectric.annotation.Implementation;
+import org.robolectric.annotation.Implements;
+import org.robolectric.shadows.ShadowBitmap;
 
 import java.io.IOException;
+import java.util.Arrays;
 
 /**
  * Tests for {@link com.bumptech.glide.gifdecoder.GifDecoder}.
@@ -94,6 +100,45 @@ public void testSettingDataResetsFramePointer() {
     assertEquals(-1, decoder.getCurrentFrameIndex());
   }
 
+  @Test
+  @Config(shadows = { CustomShadowBitmap.class })
+  public void testFirstFrameMustUsingLastFrameDispose() throws IOException {
+    byte[] data = TestUtil.resourceToBytes(getClass(), "transparent_dispose.gif");
+    GifHeaderParser headerParser = new GifHeaderParser();
+    headerParser.setData(data);
+    GifHeader header = headerParser.parseHeader();
+    GifDecoder decoder = new GifDecoder(provider);
+    decoder.setData(header, data);
+    decoder.advance();
+    Bitmap firstFrame = decoder.getNextFrame();
+    decoder.advance();
+    decoder.getNextFrame();
+    decoder.advance();
+    Bitmap firstFrameTwice = decoder.getNextFrame();
+    assertTrue(Arrays.equals((((CustomShadowBitmap) shadowOf(firstFrame))).getPixels(),
+        (((CustomShadowBitmap) shadowOf(firstFrameTwice))).getPixels()));
+  }
+
+  /**
+   * Preserve generated bitmap data for checking.
+   */
+  @Implements(Bitmap.class)
+  public static class CustomShadowBitmap extends ShadowBitmap {
+
+    private int[] pixels;
+
+    @Implementation
+    public void setPixels(int[] pixels, int offset, int stride,
+        int x, int y, int width, int height) {
+      this.pixels = new int[pixels.length];
+      System.arraycopy(pixels, 0, this.pixels, 0, this.pixels.length);
+    }
+
+    public int[] getPixels() {
+      return pixels;
+    }
+  }
+
   private static class MockProvider implements GifDecoder.BitmapProvider {
 
     @NonNull