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Commit 0d30ebca authored by Rakesh Kumar's avatar Rakesh Kumar
Browse files

Fix how ExifInterface creates VP8X chunks for WebP files 

The current code reads alpha into an int, doesn't shift it back to the
least-significant-bit, and then shifts that value 4 more bits before
writing to the VP8X 'flags' byte. This results in setting the MSB of the
flags byte, which is a reserved bit that must always be zero, resulting
in an invalid file.

VP8X part of WebP spec:
https://developers.google.com/speed/webp/docs/riff_container#extended_file_format

Test: ExifInterfaceTest (after removing the suppression for this bug)

Bug: 253622642
Change-Id: I42469a479c94442eb395124c4eac174bd9ab6e09
parent e3e6fa1e

media/java/android/media/ExifInterface.java

+6 −4
Original line number Diff line number Diff line
@@ -3825,7 +3825,7 @@ public class ExifInterface { 
                    int widthAndHeight = 0;

                    int width = 0;

                    int height = 0;

                    int alpha = 0;

                    boolean alpha = false;

                    // Save VP8 frame data for later

                    byte[] vp8Frame = new byte[3];
@@ -3860,7 +3860,7 @@ public class ExifInterface { 
                        width = ((widthAndHeight << 18) >> 18) + 1;

                        height = ((widthAndHeight << 4) >> 18) + 1;

                        // Retrieve alpha bit

                        alpha = widthAndHeight & (1 << 3);

                        alpha = (widthAndHeight & (1 << 28)) != 0;

                        bytesToRead -= (1 /* VP8L signature */ + 4);

                    }
@@ -3868,10 +3868,12 @@ public class ExifInterface { 
                    nonHeaderOutputStream.write(WEBP_CHUNK_TYPE_VP8X);

                    nonHeaderOutputStream.writeInt(WEBP_CHUNK_TYPE_VP8X_DEFAULT_LENGTH);

                    byte[] data = new byte[WEBP_CHUNK_TYPE_VP8X_DEFAULT_LENGTH];

                    // ALPHA flag

                    if (alpha) {

                        data[0] = (byte) (data[0] | (1 << 4));

                    }

                    // EXIF flag

                    data[0] = (byte) (data[0] | (1 << 3));

                    // ALPHA flag

                    data[0] = (byte) (data[0] | (alpha << 4));

                    // VP8X stores Width - 1 and Height - 1 values

                    width -= 1;

                    height -= 1;