Interlaced gifs without the iterator
BUG=skia:
Review URL: https://codereview.chromium.org/1315583003
diff --git a/gyp/codec.gyp b/gyp/codec.gyp
index b34c85e..a9a55d5 100644
--- a/gyp/codec.gyp
+++ b/gyp/codec.gyp
@@ -41,7 +41,6 @@
'../src/codec/SkCodec_libico.cpp',
'../src/codec/SkCodec_libpng.cpp',
'../src/codec/SkCodec_wbmp.cpp',
- '../src/codec/SkGifInterlaceIter.cpp',
'../src/codec/SkJpegCodec.cpp',
'../src/codec/SkJpegDecoderMgr.cpp',
'../src/codec/SkJpegUtility_codec.cpp',
diff --git a/src/codec/SkCodec_libgif.cpp b/src/codec/SkCodec_libgif.cpp
index 20a5572..3e78f23 100644
--- a/src/codec/SkCodec_libgif.cpp
+++ b/src/codec/SkCodec_libgif.cpp
@@ -9,7 +9,6 @@
#include "SkCodecPriv.h"
#include "SkColorPriv.h"
#include "SkColorTable.h"
-#include "SkGifInterlaceIter.h"
#include "SkStream.h"
#include "SkSwizzler.h"
#include "SkUtils.h"
@@ -116,6 +115,31 @@
return SK_MaxU32;
}
+static inline uint32_t ceil_div(uint32_t a, uint32_t b) {
+ return (a + b - 1) / b;
+}
+
+/*
+ * Gets the output row corresponding to the encoded row for interlaced gifs
+ */
+static uint32_t get_output_row_interlaced(uint32_t encodedRow, uint32_t height) {
+ SkASSERT(encodedRow < height);
+ // First pass
+ if (encodedRow * 8 < height) {
+ return encodedRow * 8;
+ }
+ // Second pass
+ if (encodedRow * 4 < height) {
+ return 4 + 8 * (encodedRow - ceil_div(height, 8));
+ }
+ // Third pass
+ if (encodedRow * 2 < height) {
+ return 2 + 4 * (encodedRow - ceil_div(height, 4));
+ }
+ // Fourth pass
+ return 1 + 2 * (encodedRow - ceil_div(height, 2));
+}
+
/*
* Read enough of the stream to initialize the SkGifCodec.
* Returns a bool representing success or failure.
@@ -409,18 +433,14 @@
// Check the interlace flag and iterate over rows of the input
if (fGif->Image.Interlace) {
- // In interlace mode, the rows of input are rearranged in
- // the output image. We use an iterator to take care of
- // the rearranging.
- SkGifInterlaceIter iter(innerHeight);
for (int32_t y = 0; y < innerHeight; y++) {
if (GIF_ERROR == DGifGetLine(fGif, buffer.get(), innerWidth)) {
// Recover from error by filling remainder of image
if (!skipBackground) {
memset(buffer.get(), fillIndex, innerWidth);
for (; y < innerHeight; y++) {
- void* dstRow = SkTAddOffset<void>(dst,
- dstRowBytes * iter.nextY());
+ void* dstRow = SkTAddOffset<void>(dst, dstRowBytes *
+ get_output_row_interlaced(y, innerHeight));
swizzler->swizzle(dstRow, buffer.get());
}
}
@@ -428,7 +448,8 @@
"Could not decode line %d of %d.\n",
y, height - 1).c_str(), kIncompleteInput);
}
- void* dstRow = SkTAddOffset<void>(dst, dstRowBytes * iter.nextY());
+ void* dstRow = SkTAddOffset<void>(dst,
+ dstRowBytes * get_output_row_interlaced(y, innerHeight));
swizzler->swizzle(dstRow, buffer.get());
}
} else {
diff --git a/src/codec/SkGifInterlaceIter.cpp b/src/codec/SkGifInterlaceIter.cpp
deleted file mode 100644
index 3a87f695..0000000
--- a/src/codec/SkGifInterlaceIter.cpp
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright 2015 The Android Open Source Project
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkGifInterlaceIter.h"
-
-static const uint8_t kStartingInterlaceYValues[] = { 0, 4, 2, 1 };
-static const uint8_t kDeltaInterlaceYValues[] = { 8, 8, 4, 2 };
-
-SkGifInterlaceIter::SkGifInterlaceIter(int height) : fHeight(height) {
- fStartYPtr = kStartingInterlaceYValues;
- fDeltaYPtr = kDeltaInterlaceYValues;
-
- fCurrY = *fStartYPtr++;
- fDeltaY = *fDeltaYPtr++;
-}
-
-void SkGifInterlaceIter::prepareY() {
- int32_t y = fCurrY + fDeltaY;
-
- // Iterate through fStartYPtr until a valid row is found.
- // This ensures that we do not move past the height of the small images.
- while (y >= fHeight) {
- if (kStartingInterlaceYValues +
- SK_ARRAY_COUNT(kStartingInterlaceYValues) == fStartYPtr) {
- // Now we have iterated over the entire image. Forbid any
- // subsequent calls to nextY().
- SkDEBUGCODE(fStartYPtr = nullptr;)
- SkDEBUGCODE(fDeltaYPtr = nullptr;)
- y = 0;
- } else {
- y = *fStartYPtr++;
- fDeltaY = *fDeltaYPtr++;
- }
- }
- fCurrY = y;
-}
-
-int32_t SkGifInterlaceIter::nextY() {
- SkASSERT(fStartYPtr);
- SkASSERT(fDeltaYPtr);
- int32_t y = fCurrY;
- prepareY();
- return y;
-}
diff --git a/src/codec/SkGifInterlaceIter.h b/src/codec/SkGifInterlaceIter.h
deleted file mode 100644
index 970cd49..0000000
--- a/src/codec/SkGifInterlaceIter.h
+++ /dev/null
@@ -1,35 +0,0 @@
-/*
- * Copyright 2015 The Android Open Source Project
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#include "SkTypes.h"
-
-/*
- * Helper class to determine the destination y-values for interlaced gifs
- */
-class SkGifInterlaceIter : SkNoncopyable {
-public:
-
- explicit SkGifInterlaceIter(int32_t height);
-
- /*
- * Get the next destination y-value
- */
- int32_t nextY();
-
-private:
-
- /*
- * Updates the iterator to prepare the next y-value
- */
- void prepareY();
-
- const int32_t fHeight;
- int32_t fCurrY;
- int32_t fDeltaY;
- const uint8_t* fStartYPtr;
- const uint8_t* fDeltaYPtr;
-};