Improve the Codec_end test and add fixes

Better imitate the original Android bug. Create a stream with
multiple images in it, and verify that it successfully decodes after
decoding once.

This exposes a bug in SkPngCodec, which did not work for interlaced
images.

Test more formats that also happen to succeed: ICO, BMP, and WBMP

This explicitly does *not* attempt to fix sampled or subset
decodes, which already stopped early when decoding as an
optimization.

Change-Id: Ib0b8918f14ba3fb0fa31e9c71c8100dcbeeb465f
Reviewed-on: https://skia-review.googlesource.com/14104
Reviewed-by: Matt Sarett <msarett@google.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index 1f69159ee6..b6f418fd49 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -647,7 +647,7 @@ private:
     // as expensive as the subset version of non-interlaced, but it still does extra
     // work.
     void interlacedRowCallback(png_bytep row, int rowNum, int pass) {
-        if (rowNum < fFirstRow || rowNum > fLastRow) {
+        if (rowNum < fFirstRow || rowNum > fLastRow || fInterlacedComplete) {
             // Ignore this row
             return;
         }
@@ -663,12 +663,16 @@ private:
         } else {
             SkASSERT(fLinesDecoded == fLastRow - fFirstRow + 1);
             if (fNumberPasses - 1 == pass && rowNum == fLastRow) {
-                // Last pass, and we have read all of the rows we care about. Note that
-                // we do not care about reading anything beyond the end of the image (or
-                // beyond the last scanline requested).
+                // Last pass, and we have read all of the rows we care about.
                 fInterlacedComplete = true;
-                // Fake error to stop decoding scanlines.
-                longjmp(PNG_JMPBUF(this->png_ptr()), kStopDecoding);
+                if (fLastRow != this->getInfo().height() - 1 ||
+                        (this->swizzler() && this->swizzler()->sampleY() != 1)) {
+                    // Fake error to stop decoding scanlines. Only stop if we're not decoding the
+                    // whole image, in which case processing the rest of the image might be
+                    // expensive. When decoding the whole image, read through the IEND chunk to
+                    // preserve Android behavior of leaving the input stream in the right place.
+                    longjmp(PNG_JMPBUF(this->png_ptr()), kStopDecoding);
+                }
             }
         }
     }