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-rw-r--r--image/Downscaler.cpp14
1 files changed, 10 insertions, 4 deletions
diff --git a/image/Downscaler.cpp b/image/Downscaler.cpp
index 18f09c596..2ded487a5 100644
--- a/image/Downscaler.cpp
+++ b/image/Downscaler.cpp
@@ -231,6 +231,7 @@ Downscaler::CommitRow()
int32_t inLineToRead = filterOffset + mLinesInBuffer;
MOZ_ASSERT(mCurrentInLine <= inLineToRead, "Reading past end of input");
if (mCurrentInLine == inLineToRead) {
+ MOZ_RELEASE_ASSERT(mLinesInBuffer < mWindowCapacity, "Need more rows than capacity!");
skia::ConvolveHorizontally(mRowBuffer.get(), *mXFilter,
mWindow[mLinesInBuffer++], mHasAlpha,
supports_sse2() || supports_mmi());
@@ -239,7 +240,7 @@ Downscaler::CommitRow()
MOZ_ASSERT(mCurrentOutLine < mTargetSize.height,
"Writing past end of output");
- while (mLinesInBuffer == filterLength) {
+ while (mLinesInBuffer >= filterLength) {
DownscaleInputLine();
if (mCurrentOutLine == mTargetSize.height) {
@@ -340,9 +341,14 @@ Downscaler::DownscaleInputLine()
// Shift the buffer. We're just moving pointers here, so this is cheap.
mLinesInBuffer -= diff;
- mLinesInBuffer = max(mLinesInBuffer, 0);
- for (int32_t i = 0; i < mLinesInBuffer; ++i) {
- swap(mWindow[i], mWindow[filterLength - mLinesInBuffer + i]);
+ mLinesInBuffer = min(max(mLinesInBuffer, 0), mWindowCapacity);
+
+ // If we already have enough rows to satisfy the filter, there is no need
+ // to swap as we won't be writing more before the next convolution.
+ if (filterLength > mLinesInBuffer) {
+ for (int32_t i = 0; i < mLinesInBuffer; ++i) {
+ swap(mWindow[i], mWindow[filterLength - mLinesInBuffer + i]);
+ }
}
}