Move all knowledge of X sampling into SkScaledCodec

Prior to this CL, each SkCodec subclass that allows sampling does an
extra check in onStartScanlineDecode to determine whether the X dimension
is supported for sampling. Remove this check, and provide a way for
SkScaledCodec to directly access the SkSwizzler, and update it to do
sampling. This way, the SkCodec knows nothing of sampling, but we can
still save the extra step of sampling afterwards.

FIXME: SkBmpRLECodec still calls SkScaledCodec::DimensionsSupported. It
seems like it could directly support sampling, rather than dealing with
SkScaledCodec (partially).

Add a new base class for SkSwizzler. It allows updating the swizzler
after it was created, which is done by SkScaledCodec. Modify SkSwizzler's
constructor/factory function to stop taking any info about sampling,
assume the sample size is one, and move modifying that into a virtual
function overridden from the base class.

BUG=skia:4284

Review URL: https://codereview.chromium.org/1372973002

1 files changed, 6 insertions, 0 deletions

diff --git a/src/codec/SkBmpRLECodec.h b/src/codec/SkBmpRLECodec.h
index ea2c2b6bab..8721969a85 100644
--- a/src/codec/SkBmpRLECodec.h
+++ b/src/codec/SkBmpRLECodec.h
@@ -8,6 +8,7 @@
 #include "SkBmpCodec.h"
 #include "SkColorTable.h"
 #include "SkImageInfo.h"
+#include "SkSampler.h"
 #include "SkTypes.h"
 
 /*
@@ -39,6 +40,8 @@ public:
             uint32_t offset, SkCodec::SkScanlineOrder rowOrder,
             size_t RLEBytes);
 
+    int setSampleX(int);
+
 protected:
 
     Result onGetPixels(const SkImageInfo& dstInfo, void* dst,
@@ -84,6 +87,8 @@ private:
     Result decodeRows(const SkImageInfo& dstInfo, void* dst, size_t dstRowBytes,
                       const Options& opts) override;
 
+    SkSampler* getSampler() override;
+
     SkAutoTUnref<SkColorTable>          fColorTable;    // owned
     const uint32_t                      fNumColors;
     const uint32_t                      fBytesPerColor;
@@ -92,6 +97,7 @@ private:
     size_t                              fRLEBytes;
     uint32_t                            fCurrRLEByte;
     int                                 fSampleX;
+    SkAutoTDelete<SkSampler>            fSampler;
 
     typedef SkBmpCodec INHERITED;
 };