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SkPngCodec clean-ups

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Use png_read_row() instead of png_read_rows(1).
All png_read_rows() does is call png_read_row() in
a loop.  This comes from Leon's comment in:
https://codereview.chromium.org/1671003004/

Also there is a bit of refactoring.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1675843002

Review URL: https://codereview.chromium.org/1675843002
This commit is contained in:
msarett 2016-02-05 15:13:12 -08:00 committed by Commit bot
parent 52b64619d9
commit 60dcd3cb85
1 changed files with 21 additions and 29 deletions
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50
src/codec/SkPngCodec.cpp
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@ -478,6 +478,12 @@ SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void*
if (result != kSuccess) {
return result;
}
const int width = requestedInfo.width();
const int height = requestedInfo.height();
const int bpp = SkSwizzler::BytesPerPixel(fSrcConfig);
const size_t srcRowBytes = width * bpp;
// FIXME: Could we use the return value of setjmp to specify the type of
// error?
int row = 0;
@ -487,7 +493,7 @@ SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void*
// Assume that any error that occurs while reading rows is caused by an incomplete input.
if (fNumberPasses > 1) {
// FIXME (msarett): Handle incomplete interlaced pngs.
return kInvalidInput;
return (row == height) ? kSuccess : kInvalidInput;
}
// FIXME: We do a poor job on incomplete pngs compared to other decoders (ex: Chromium,
// Ubuntu Image Viewer). This is because we use the default buffer size in libpng (8192
@ -499,54 +505,42 @@ SkCodec::Result SkPngCodec::onGetPixels(const SkImageInfo& requestedInfo, void*
// made a partial read.
// Making our buffer size smaller improves our incomplete decodes, but what impact does
// it have on regular decode performance? Should we investigate using a different API
// instead of png_read_row(s)? Chromium uses png_process_data.
// instead of png_read_row? Chromium uses png_process_data.
*rowsDecoded = row;
return kIncompleteInput;
return (row == height) ? kSuccess : kIncompleteInput;
}
// FIXME: We could split these out based on subclass.
void* dstRow = dst;
if (fNumberPasses > 1) {
const int width = requestedInfo.width();
const int height = requestedInfo.height();
const int bpp = SkSwizzler::BytesPerPixel(fSrcConfig);
const size_t srcRowBytes = width * bpp;
storage.reset(width * height * bpp);
storage.reset(height * srcRowBytes);
uint8_t* const base = storage.get();
for (int i = 0; i < fNumberPasses; i++) {
uint8_t* srcRow = base;
for (int y = 0; y < height; y++) {
uint8_t* bmRow = srcRow;
png_read_rows(fPng_ptr, &bmRow, nullptr, 1);
png_read_row(fPng_ptr, srcRow, nullptr);
srcRow += srcRowBytes;
}
}
// Now swizzle it.
uint8_t* srcRow = base;
for (int y = 0; y < height; y++) {
for (; row < height; row++) {
fSwizzler->swizzle(dstRow, srcRow);
dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
srcRow += srcRowBytes;
}
} else {
storage.reset(requestedInfo.width() * SkSwizzler::BytesPerPixel(fSrcConfig));
storage.reset(srcRowBytes);
uint8_t* srcRow = storage.get();
for (; row < requestedInfo.height(); row++) {
png_read_rows(fPng_ptr, &srcRow, nullptr, 1);
// FIXME: Only call IsOpaque once, outside the loop. Same for onGetScanlines.
for (; row < height; row++) {
png_read_row(fPng_ptr, srcRow, nullptr);
fSwizzler->swizzle(dstRow, srcRow);
dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
}
}
if (setjmp(png_jmpbuf(fPng_ptr))) {
// We've already read all the scanlines. This is a success.
return kSuccess;
}
// read rest of file, and get additional comment and time chunks in info_ptr
png_read_end(fPng_ptr, fInfo_ptr);
@ -598,7 +592,7 @@ public:
void* dstRow = dst;
for (; row < count; row++) {
png_read_rows(this->png_ptr(), &fSrcRow, nullptr, 1);
png_read_row(this->png_ptr(), fSrcRow, nullptr);
this->swizzler()->swizzle(dstRow, fSrcRow);
dstRow = SkTAddOffset<void>(dstRow, rowBytes);
}
@ -612,11 +606,9 @@ public:
SkCodecPrintf("setjmp long jump!\n");
return false;
}
//there is a potential tradeoff of memory vs speed created by putting this in a loop.
//calling png_read_rows in a loop is insignificantly slower than calling it once with count
//as png_read_rows has it's own loop which calls png_read_row count times.
for (int row = 0; row < count; row++) {
png_read_rows(this->png_ptr(), &fSrcRow, nullptr, 1);
png_read_row(this->png_ptr(), fSrcRow, nullptr);
}
return true;
}
@ -700,17 +692,17 @@ public:
for (int i = 0; i < this->numberPasses(); i++) {
// read rows we planned to skip into garbage row
for (int y = 0; y < startRow; y++){
png_read_rows(this->png_ptr(), &fGarbageRowPtr, nullptr, 1);
png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
}
// read rows we care about into buffer
srcRow = storagePtr;
for (int y = 0; y < count; y++) {
png_read_rows(this->png_ptr(), &srcRow, nullptr, 1);
png_read_row(this->png_ptr(), srcRow, nullptr);
srcRow += fSrcRowBytes;
}
// read rows we don't want into garbage buffer
for (int y = 0; y < fHeight - startRow - count; y++) {
png_read_rows(this->png_ptr(), &fGarbageRowPtr, nullptr, 1);
png_read_row(this->png_ptr(), fGarbageRowPtr, nullptr);
}
}
//swizzle the rows we care about