| commit | e7aeeae0c89f5bae76ba263b1ab2b82c56ad32a3 | [log] [tgz] |
|---|---|---|
| author | Nigel Tao <nigeltao@golang.org> | Mon Apr 22 23:36:32 2024 +1000 |
| committer | Nigel Tao <nigeltao@golang.org> | Thu Apr 25 00:46:29 2024 +0000 |
| tree | 8323867b3672c9fb795a548d5a165192b44203ac | |
| parent | 799968dfc3b9121019b752a9110489baa71a4355 [diff] |
image/jpeg: ignore garbage bytes before a RST marker Well-formed JPEG images will not have garbage bytes. However, for corrupted JPEG images, the RST (restart) mechanism is specifically designed so that a decoder can re-synchronize to an upcoming restartable MCU (Minimum Coded Unit, e.g. 16x16 block of pixels) boundary and resume decoding. Even if the resultant image isn't perfect, a 98%-good image is better than a fatal error. Every JPEG marker is encoded in two bytes, the first of which is 0xFF. There are 8 possible RST markers, cycling as "0xFF 0xD0", "0xFF 0xD1", ..., "0xFF 0xD7". Suppose that, our decoder is expecting "0xFF 0xD1". Before this commit, Go's image/jpeg package would accept only two possible inputs: a well-formed "0xFF 0xD1" or one very specific pattern of spec non-compliance, "0xFF 0x00 0xFF 0xD1". After this commit, it is more lenient, similar to libjpeg's jdmarker.c's next_marker function. https://github.com/libjpeg-turbo/libjpeg-turbo/blob/2dfe6c0fe9e18671105e94f7cbf044d4a1d157e6/jdmarker.c#L892-L935 The new testdata file was created by: $ convert video-001.png a.ppm $ cjpeg -restart 2 a.ppm > video-001.restart2.jpeg $ rm a.ppm Fixes #40130 Change-Id: Ic598a5f489f110d6bd63e0735200fb6acac3aca3 Reviewed-on: https://go-review.googlesource.com/c/go/+/580755 Reviewed-by: Ian Lance Taylor <iant@google.com> LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Joedian Reid <joedian@google.com>
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