Make Jpeg decoding more fault resistant.

src/images/SkImageDecoder_libjpeg.cpp

Index: src/images/SkImageDecoder_libjpeg.cpp
diff --git a/src/images/SkImageDecoder_libjpeg.cpp b/src/images/SkImageDecoder_libjpeg.cpp
index 3b3ea887e3cde437d7469d2a43126a2cb604a6eb..28c3edeace5668a157b98d53d52294c3bd75282c 100644
--- a/src/images/SkImageDecoder_libjpeg.cpp
+++ b/src/images/SkImageDecoder_libjpeg.cpp
@@ -19,6 +19,10 @@
 #include "SkRect.h"
 #include "SkCanvas.h"
 
+#if defined(SK_DEBUG)
+#include "SkRTConf.h"  // SK_CONF_DECLARE
+#endif  // defined(SK_DEBUG)
+
 #include <stdio.h>
 extern "C" {
     #include "jpeglib.h"
@@ -35,6 +39,12 @@ extern "C" {
 // If ANDROID_RGB is defined by in the jpeg headers it indicates that jpeg offers
 // support for two additional formats (1) JCS_RGBA_8888 and (2) JCS_RGB_565.
 
+#if defined(SK_DEBUG)
+SK_CONF_DECLARE(bool, c_suppressJPEGImageDecoderWarnings,
+    "images.jpeg.suppressDecoderWarnings", false,
+    "Suppress most JPG warnings when calling decode functions.");
+#endif  // defined(SK_DEBUG)
+
 //////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////
 
@@ -54,12 +64,27 @@ static void overwrite_mem_buffer_size(jpeg_decompress_struct* cinfo) {
 //////////////////////////////////////////////////////////////////////////
 //////////////////////////////////////////////////////////////////////////
 
+static void do_nothing_emit_message(jpeg_common_struct*, int) {
+    /* do nothing */
+}
+
 static void initialize_info(jpeg_decompress_struct* cinfo, skjpeg_source_mgr* src_mgr) {
     SkASSERT(cinfo != NULL);
     SkASSERT(src_mgr != NULL);
     jpeg_create_decompress(cinfo);
     overwrite_mem_buffer_size(cinfo);
     cinfo->src = src_mgr;
+#if defined(SK_DEBUG)
+    /* To suppress warnings with a SK_DEBUG binary, set the
+     * environment variable "skia_images_jpeg_suppressDecoderWarnings"
+     * to "true".  Inside a program that links to skia:
+     * SK_CONF_SET("images.jpeg.suppressDecoderWarnings", true); */
+    if (c_suppressJPEGImageDecoderWarnings) {
+        cinfo->err->emit_message = &do_nothing_emit_message;
+    }
+#else  // Always suppress in release mode.
+    cinfo->err->emit_message = &do_nothing_emit_message;
+#endif  //defined(SK_DEBUG)
 }
 
 #ifdef SK_BUILD_FOR_ANDROID
@@ -556,7 +581,7 @@ bool SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
             // if row_count == 0, then we didn't get a scanline, so abort.
             // if we supported partial images, we might return true in this case
             if (0 == row_count) {
-                return return_false(cinfo, *bm, "read_scanlines");
+                return true;

[scroggo, 2013/10/02 17:05:04]

The remaining rows will still be uninitialized.

             }
             if (this->shouldCancelDecode()) {
                 return return_false(cinfo, *bm, "shouldCancelDecode");
@@ -606,7 +631,7 @@ bool SkJPEGImageDecoder::onDecode(SkStream* stream, SkBitmap* bm, Mode mode) {
         JSAMPLE* rowptr = (JSAMPLE*)srcRow;
         int row_count = jpeg_read_scanlines(&cinfo, &rowptr, 1);
         if (0 == row_count) {
-            return return_false(cinfo, *bm, "read_scanlines");
+            return true;

[scroggo, 2013/10/02 17:05:04]

Ditto

         }
         if (this->shouldCancelDecode()) {
             return return_false(cinfo, *bm, "shouldCancelDecode");
@@ -788,7 +813,7 @@ bool SkJPEGImageDecoder::onDecodeSubset(SkBitmap* bm, const SkIRect& region) {
             // if row_count == 0, then we didn't get a scanline, so abort.
             // if we supported partial images, we might return true in this case
             if (0 == rowCount) {
-                return return_false(*cinfo, bitmap, "read_scanlines");
+                return true;

[scroggo, 2013/10/02 17:05:04]

Ditto

             }
             if (this->shouldCancelDecode()) {
                 return return_false(*cinfo, bitmap, "shouldCancelDecode");
@@ -845,7 +870,7 @@ bool SkJPEGImageDecoder::onDecodeSubset(SkBitmap* bm, const SkIRect& region) {
         JSAMPLE* rowptr = (JSAMPLE*)srcRow;
         int row_count = jpeg_read_tile_scanline(cinfo, fImageIndex->huffmanIndex(), &rowptr);
         if (0 == row_count) {
-            return return_false(*cinfo, bitmap, "read_scanlines");
+            return true;

[scroggo, 2013/10/02 17:05:04]

Ditto

         }
         if (this->shouldCancelDecode()) {
             return return_false(*cinfo, bitmap, "shouldCancelDecode");