Bug 1191114 (Part 1) - Always detect HAS_TRANSPARENCY during the metadata decode. r=tn

--HG--
extra : rebase_source : 97c8568f33abd1f2a8d9ef5679ce3ac904f0758f

image/decoders/nsBMPDecoder.cpp

@@ -369,6 +369,15 @@ nsBMPDecoder::WriteInternal(const char* aBuffer, uint32_t aCount)
         return;
       }
 
+      // We treat BMPs as transparent if they're 32bpp and alpha is enabled, but
+      // also if they use RLE encoding, because the 'delta' mode can skip pixels
+      // and cause implicit transparency.
+      if ((mBIH.compression == BMPINFOHEADER::RLE8) ||
+          (mBIH.compression == BMPINFOHEADER::RLE4) ||
+          (mBIH.bpp == 32 && mUseAlphaData)) {
+        PostHasTransparency();
+      }
+
       // We have the size. If we're doing a metadata decode, we're done.
       if (IsMetadataDecode()) {
         return;

image/decoders/nsGIFDecoder2.cpp

@@ -50,6 +50,8 @@ mailing address.
 #include <algorithm>
 #include "mozilla/Telemetry.h"
 
+using namespace mozilla::gfx;
+
 namespace mozilla {
 namespace image {
 
@@ -161,6 +163,27 @@ nsGIFDecoder2::BeginGIF()
   PostSize(mGIFStruct.screen_width, mGIFStruct.screen_height);
 }
 
+void
+nsGIFDecoder2::CheckForTransparency(IntRect aFrameRect)
+{
+  // Check if the image has a transparent color in its palette.
+  if (mGIFStruct.is_transparent) {
+    PostHasTransparency();
+    return;
+  }
+
+  if (mGIFStruct.images_decoded > 0) {
+    return;  // We only care about first frame padding below.
+  }
+
+  // If we need padding on the first frame, that means we don't draw into part
+  // of the image at all. Report that as transparency.
+  IntRect imageRect(0, 0, mGIFStruct.screen_width, mGIFStruct.screen_height);
+  if (!imageRect.IsEqualEdges(aFrameRect)) {
+    PostHasTransparency();
+  }
+}
+
 //******************************************************************************
 nsresult
 nsGIFDecoder2::BeginImageFrame(uint16_t aDepth)
@@ -170,13 +193,14 @@ nsGIFDecoder2::BeginImageFrame(uint16_t aDepth)
   gfx::SurfaceFormat format;
   if (mGIFStruct.is_transparent) {
     format = gfx::SurfaceFormat::B8G8R8A8;
-    PostHasTransparency();
   } else {
     format = gfx::SurfaceFormat::B8G8R8X8;
   }
 
-  nsIntRect frameRect(mGIFStruct.x_offset, mGIFStruct.y_offset,
-                      mGIFStruct.width, mGIFStruct.height);
+  IntRect frameRect(mGIFStruct.x_offset, mGIFStruct.y_offset,
+                    mGIFStruct.width, mGIFStruct.height);
+
+  CheckForTransparency(frameRect);
 
   // Use correct format, RGB for first frame, PAL for following frames
   // and include transparency to allow for optimization of opaque images
@@ -186,12 +210,6 @@ nsGIFDecoder2::BeginImageFrame(uint16_t aDepth)
     rv = AllocateFrame(mGIFStruct.images_decoded, GetSize(),
                        frameRect, format, aDepth);
   } else {
-    if (!nsIntRect(nsIntPoint(), GetSize()).IsEqualEdges(frameRect)) {
-      // We need padding on the first frame, which means that we don't draw into
-      // part of the image at all. Report that as transparency.
-      PostHasTransparency();
-    }
-
     // Regardless of depth of input, the first frame is decoded into 24bit RGB.
     rv = AllocateFrame(mGIFStruct.images_decoded, GetSize(),
                        frameRect, format);
@@ -689,12 +707,6 @@ nsGIFDecoder2::WriteInternal(const char* aBuffer, uint32_t aCount)
       mGIFStruct.screen_height = GETINT16(q + 2);
       mGIFStruct.global_colormap_depth = (q[4]&0x07) + 1;
 
-      if (IsMetadataDecode()) {
-        MOZ_ASSERT(!mGIFOpen, "Gif should not be open at this point");
-        PostSize(mGIFStruct.screen_width, mGIFStruct.screen_height);
-        return;
-      }
-
       // screen_bgcolor is not used
       //mGIFStruct.screen_bgcolor = q[5];
       // q[6] = Pixel Aspect Ratio
@@ -731,6 +743,9 @@ nsGIFDecoder2::WriteInternal(const char* aBuffer, uint32_t aCount)
     case gif_image_start:
       switch (*q) {
         case GIF_TRAILER:
+          if (IsMetadataDecode()) {
+            return;
+          }
           mGIFStruct.state = gif_done;
           break;
 
@@ -943,6 +958,9 @@ nsGIFDecoder2::WriteInternal(const char* aBuffer, uint32_t aCount)
 
         // If we were doing a metadata decode, we're done.
         if (IsMetadataDecode()) {
+          IntRect frameRect(mGIFStruct.x_offset, mGIFStruct.y_offset,
+                            mGIFStruct.width, mGIFStruct.height);
+          CheckForTransparency(frameRect);
           return;
         }
       }

image/decoders/nsGIFDecoder2.h

@@ -47,6 +47,7 @@ private:
   bool      DoLzw(const uint8_t* q);
   bool      SetHold(const uint8_t* buf, uint32_t count,
                     const uint8_t* buf2 = nullptr, uint32_t count2 = 0);
+  void      CheckForTransparency(gfx::IntRect aFrameRect);
 
   inline int ClearCode() const { return 1 << mGIFStruct.datasize; }
 

image/decoders/nsPNGDecoder.cpp

@@ -19,6 +19,8 @@
 
 #include <algorithm>
 
+using namespace mozilla::gfx;
+
 namespace mozilla {
 namespace image {
 
@@ -136,6 +138,20 @@ nsPNGDecoder::~nsPNGDecoder()
   }
 }
 
+void
+nsPNGDecoder::CheckForTransparency(SurfaceFormat aFormat,
+                                   const IntRect& aFrameRect)
+{
+  // Check if the image has a transparent color in its palette.
+  if (aFormat == SurfaceFormat::B8G8R8A8) {
+    PostHasTransparency();
+  }
+
+  // PNGs shouldn't have first-frame padding.
+  MOZ_ASSERT_IF(mNumFrames == 0,
+                IntRect(IntPoint(), GetSize()).IsEqualEdges(aFrameRect));
+}
+
 // CreateFrame() is used for both simple and animated images
 nsresult
 nsPNGDecoder::CreateFrame(png_uint_32 aXOffset, png_uint_32 aYOffset,
@@ -145,17 +161,8 @@ nsPNGDecoder::CreateFrame(png_uint_32 aXOffset, png_uint_32 aYOffset,
   MOZ_ASSERT(HasSize());
   MOZ_ASSERT(!IsMetadataDecode());
 
-  if (aFormat == gfx::SurfaceFormat::B8G8R8A8) {
-    PostHasTransparency();
-  }
-
-  nsIntRect frameRect(aXOffset, aYOffset, aWidth, aHeight);
-  if (mNumFrames == 0 &&
-      !nsIntRect(nsIntPoint(), GetSize()).IsEqualEdges(frameRect)) {
-    // We need padding on the first frame, which means that we don't draw into
-    // part of the image at all. Report that as transparency.
-    PostHasTransparency();
-  }
+  IntRect frameRect(aXOffset, aYOffset, aWidth, aHeight);
+  CheckForTransparency(aFormat, frameRect);
 
   // XXX(seth): Some tests depend on the first frame of PNGs being B8G8R8A8.
   // This is something we should fix.
@@ -268,7 +275,7 @@ nsPNGDecoder::InitInternal()
 
 #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
   // Ignore unused chunks
-  if (mCMSMode == eCMSMode_Off) {
+  if (mCMSMode == eCMSMode_Off || IsMetadataDecode()) {
     png_set_keep_unknown_chunks(mPNG, 1, color_chunks, 2);
   }
 
@@ -486,12 +493,6 @@ nsPNGDecoder::info_callback(png_structp png_ptr, png_infop info_ptr)
     png_longjmp(decoder->mPNG, 1);
   }
 
-  if (decoder->IsMetadataDecode()) {
-    // We have the size, so we don't need to decode any further.
-    decoder->mSuccessfulEarlyFinish = true;
-    png_longjmp(decoder->mPNG, 1);
-  }
-
   if (color_type == PNG_COLOR_TYPE_PALETTE) {
     png_set_expand(png_ptr);
   }
@@ -594,6 +595,16 @@ nsPNGDecoder::info_callback(png_structp png_ptr, png_infop info_ptr)
     png_longjmp(decoder->mPNG, 1); // invalid number of channels
   }
 
+  if (decoder->IsMetadataDecode()) {
+    decoder->CheckForTransparency(decoder->format,
+                                  IntRect(0, 0, width, height));
+
+    // We have the size and transparency information we're looking for, so we
+    // don't need to decode any further.
+    decoder->mSuccessfulEarlyFinish = true;
+    png_longjmp(decoder->mPNG, 1);
+  }
+
 #ifdef PNG_APNG_SUPPORTED
   if (png_get_valid(png_ptr, info_ptr, PNG_INFO_acTL)) {
     png_set_progressive_frame_fn(png_ptr, nsPNGDecoder::frame_info_callback,

image/decoders/nsPNGDecoder.h

@@ -35,6 +35,9 @@ public:
                        gfx::SurfaceFormat aFormat);
   void EndImageFrame();
 
+  void CheckForTransparency(gfx::SurfaceFormat aFormat,
+                            const gfx::IntRect& aFrameRect);
+
   // Check if PNG is valid ICO (32bpp RGBA)
   // http://blogs.msdn.com/b/oldnewthing/archive/2010/10/22/10079192.aspx
   bool IsValidICO() const

image/test/mochitest/test_has_transparency.html

@@ -48,8 +48,12 @@ function testFiles() {
   // GIFs with padding on the first frame are always transparent.
   yield ["first-frame-padding.gif", true];
 
-  // JPEGs and BMPs are never transparent.
+  // JPEGs are never transparent.
   yield ["damon.jpg", false];
+
+  // Most BMPs are not transparent. (The TestMetadata GTest, which will
+  // eventually replace this test totally, has coverage for the kinds that can be
+  // transparent.)
   yield ["opaque.bmp", false];
 
   // ICO files which contain BMPs have an additional type of transparency - the