Scanline decoding for wbmp

src/codec/SkCodec_wbmp.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkCodec.h"
+#include "SkCodecPriv.h"
 #include "SkColorPriv.h"
+#include "SkColorTable.h"
 #include "SkStream.h"
 #include "SkCodec_wbmp.h"
 
+// Each bit represents a pixel, so width is actually a number of bits.
+// A row will always be stored in bytes, so we round width up to the
+// nearest multiple of 8 to get the number of bits actually in the row.
+// We then divide by 8 to convert to bytes.
+static inline size_t get_src_row_bytes(int width) {
+    return SkAlign8(width) >> 3;
+}
+
+static inline void setup_color_table(SkColorType colorType,
+        SkPMColor* colorPtr, int* colorCount) {
+    if (kIndex_8_SkColorType == colorType) {
+        colorPtr[0] = SK_ColorBLACK;
+        colorPtr[1] = SK_ColorWHITE;
+        *colorCount = 2;
+    }
+}
+
 // http://en.wikipedia.org/wiki/Variable-length_quantity
 static bool read_mbf(SkStream* stream, uint64_t* value) {
     uint64_t n = 0;
     uint8_t data;
     const uint64_t kLimit = 0xFE00000000000000;
     SkASSERT(kLimit == ~((~static_cast<uint64_t>(0)) >> 7));
     do {
         if (n & kLimit) { // Will overflow on shift by 7.
             return false;
         }
         if (stream->read(&data, 1) != 1) {
             return false;
         }
         n = (n << 7) | (data & 0x7F);
     } while (data & 0x80);
     *value = n;
     return true;
 }
 
 static bool read_header(SkStream* stream, SkISize* size) {
     uint64_t width, height;
     uint16_t data;
     if (stream->read(&data, 2) != 2 || data != 0) {
         return false;
     }
     if (!read_mbf(stream, &width) || width > 0xFFFF || !width) {
         return false;
     }
-    if (!read_mbf(stream, &height) || width > 0xFFFF || !height) {
+    if (!read_mbf(stream, &height) || height > 0xFFFF || !height) {
         return false;
     }
     if (size) {
         *size = SkISize::Make(SkToS32(width), SkToS32(height));
     }
     return true;
 }
 
-#define BLACK SkPackARGB32NoCheck(0xFF, 0, 0, 0)
-#define WHITE SkPackARGB32NoCheck(0xFF, 0xFF, 0xFF, 0xFF)
-
-#define GRAYSCALE_BLACK 0
-#define GRAYSCALE_WHITE 0xFF
-
-#define RGB565_BLACK 0
-#define RGB565_WHITE 0xFFFF
-
-static SkPMColor bit_to_pmcolor(U8CPU bit) { return bit ? WHITE : BLACK; }
-
-static uint8_t bit_to_bit(U8CPU bit) { return bit; }
-
-static uint8_t bit_to_grayscale(U8CPU bit) {
-    return bit ? GRAYSCALE_WHITE : GRAYSCALE_BLACK;
+bool SkWbmpCodec::handleRewind() {

[scroggo, 2015/08/05 17:55:37]

I'm beginning to think this should be in the base class:

bool SkCodec::rewindIfNeeded() {
  const bool needsRewind = fNeedsRewind;
  if (!needsRewind) {
    return true;
  }
  if (!fStream->rewind()) {
    return false;
  }
  return this->onRewind(); // this function is virtual
}

Then the subclasses can just say

if (!this->rewindIfNeeded()) {
  return kCouldNotRewind;
}

bool onRewind() override { // or maybe it should return SkCodec::Result?
  return read_header(...)
}

This should be in a separate CL, but if all codecs have this function, I think
this would be a cleaner, more code-shared way to do it.

[msarett, 2015/08/05 18:50:33]

+1 for this in a separate CL

[scroggo, 2015/08/05 19:35:38]

Filed skbug.com/4170

+    SkCodec::RewindState rewindState = this->rewindIfNeeded();
+    if (rewindState == kCouldNotRewind_RewindState) {
+        return false;
+    } else if (rewindState == kRewound_RewindState) {
+        (void)read_header(this->stream(), NULL);

[scroggo, 2015/08/05 17:55:37]

FWIW, in SkPngCodec, we check the return value of read_header. It certainly
should return true the second time if it returned true the first time, so maybe
this is unnecessary, but I think we should probably do the same thing
everywhere?

[msarett, 2015/08/05 18:50:33]

Agreed.  Fixed this in wbmp.

+    }
+    return true;
 }
 
-static uint16_t bit_to_rgb565(U8CPU bit) {
-    return bit ? RGB565_WHITE : RGB565_BLACK;
-}
+SkSwizzler* SkWbmpCodec::initializeSwizzler(const SkImageInfo& info,
+        const SkPMColor* ctable, const Options& opts) {
+    // TODO (msarett): Reenable support for 565 if it is desired
+    //                 skbug.com/3683
 
-typedef void (*ExpandProc)(uint8_t*, const uint8_t*, int);
-
-// TODO(halcanary): Add this functionality (grayscale and indexed output) to
-//                  SkSwizzler and use it here.
-template <typename T, T (*TRANSFORM)(U8CPU)>
-static void expand_bits_to_T(uint8_t* dstptr, const uint8_t* src, int bits) {
-    T* dst = reinterpret_cast<T*>(dstptr);
-    int bytes = bits >> 3;
-    for (int i = 0; i < bytes; i++) {
-        U8CPU mask = *src++;
-        for (int j = 0; j < 8; j++) {
-            dst[j] = TRANSFORM((mask >> (7 - j)) & 1);
-        }
-        dst += 8;
-    }
-    bits &= 7;
-    if (bits > 0) {
-        U8CPU mask = *src;
-        do {
-            *dst++ = TRANSFORM((mask >> 7) & 1);
-            mask <<= 1;
-        } while (--bits != 0);
+    // Create the swizzler based on the desired color type
+    switch (info.colorType()) {
+        case kIndex_8_SkColorType:
+        case kN32_SkColorType:
+        case kGray_8_SkColorType:
+            return SkSwizzler::CreateSwizzler(
+                    SkSwizzler::kBit, ctable, info, opts.fZeroInitialized);
+        default:
+            return NULL;
     }
 }
 
+SkCodec::Result SkWbmpCodec::readRow(uint8_t* src, size_t rowBytes) {

[scroggo, 2015/08/05 17:55:37]

Why do you need the rowBytes parameter? This is based on the source data, right?
so it should always be the same for one image/codec/SD?
____________________________________________________________________________

I think it's even weirder to call this src. It is the destination for readRow,
so I would argue that dst is better, even if the caller of readRow uses it as a
source.

You could also call it something like rowPointer or just row. (libpng, for
example, calls it row)

[msarett, 2015/08/05 18:50:33]

Let's compromise on row as the name for the first parameter.

Getting rid of the second parameter by making fSrcRowBytes a field of codec.

+  if (this->stream()->read(src, rowBytes) != rowBytes) {

[scroggo, 2015/08/05 17:55:37]

nit: we use four space indents (Ah, I think you copied the code from my
suggestion? I just use two spaces in comments because of the limited room, and
the fact that "tab" does not get converted to spaces.)

[msarett, 2015/08/05 18:50:33]

Yup it's fixed now.

+    return kIncompleteInput;
+  }
+  return kSuccess;
+}
+
 SkWbmpCodec::SkWbmpCodec(const SkImageInfo& info, SkStream* stream)
-    : INHERITED(info, stream) {}
+    : INHERITED(info, stream)
+{}
 
 SkEncodedFormat SkWbmpCodec::onGetEncodedFormat() const {
     return kWBMP_SkEncodedFormat;
 }
 
 SkCodec::Result SkWbmpCodec::onGetPixels(const SkImageInfo& info,
-                                         void* pixels,
+                                         void* dst,
                                          size_t rowBytes,
                                          const Options& options,
                                          SkPMColor ctable[],
                                          int* ctableCount) {
-    SkCodec::RewindState rewindState = this->rewindIfNeeded();
-    if (rewindState == kCouldNotRewind_RewindState) {
+    if (!this->handleRewind()) {
         return kCouldNotRewind;
-    } else if (rewindState == kRewound_RewindState) {
-        (void)read_header(this->stream(), NULL);
     }
     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }
     if (info.dimensions() != this->getInfo().dimensions()) {
         return kInvalidScale;
     }
-    ExpandProc proc = NULL;
-    switch (info.colorType()) {
-        case kGray_8_SkColorType:
-            proc = expand_bits_to_T<uint8_t, bit_to_grayscale>;
-            break;
-        case kN32_SkColorType:
-            proc = expand_bits_to_T<SkPMColor, bit_to_pmcolor>;
-            break;
-        case kIndex_8_SkColorType:
-            ctable[0] = BLACK;
-            ctable[1] = WHITE;
-            *ctableCount = 2;
-            proc = expand_bits_to_T<uint8_t, bit_to_bit>;
-            break;
-        case kRGB_565_SkColorType:
-            proc = expand_bits_to_T<uint16_t, bit_to_rgb565>;
-            break;
-        default:
-            return kInvalidConversion;
+
+    // Prepare a color table if necessary
+    setup_color_table(info.colorType(), ctable, ctableCount);
+
+
+    // Initialize the swizzler
+    SkAutoTDelete<SkSwizzler> swizzler(this->initializeSwizzler(info, ctable, options));
+    if (NULL == swizzler.get()) {
+        return kInvalidConversion;
     }
+
+    // Perform the decode
     SkISize size = info.dimensions();
-    uint8_t* dst = static_cast<uint8_t*>(pixels);
-    size_t srcRowBytes = SkAlign8(size.width()) >> 3;
+    size_t srcRowBytes = get_src_row_bytes(this->getInfo().width());
     SkAutoTMalloc<uint8_t> src(srcRowBytes);
+    void* dstRow = dst;
     for (int y = 0; y < size.height(); ++y) {
-        if (this->stream()->read(src.get(), srcRowBytes) != srcRowBytes) {
-            return kIncompleteInput;
+        Result rowResult = this->readRow(src.get(), srcRowBytes);
+        if (kSuccess != rowResult) {
+            return rowResult;
         }
-        proc(dst, src.get(), size.width());
-        dst += rowBytes;
+        swizzler->swizzle(dstRow, src.get());
+        dstRow = SkTAddOffset<void>(dstRow, rowBytes);
     }
     return kSuccess;
 }
 
 bool SkWbmpCodec::IsWbmp(SkStream* stream) {
     return read_header(stream, NULL);
 }
 
 SkCodec* SkWbmpCodec::NewFromStream(SkStream* stream) {
     SkAutoTDelete<SkStream> streamDeleter(stream);
     SkISize size;
     if (!read_header(stream, &size)) {
         return NULL;
     }
-    SkImageInfo info =
-            SkImageInfo::Make(size.width(), size.height(), kGray_8_SkColorType,
-                              kOpaque_SkAlphaType);
+    SkImageInfo info = SkImageInfo::Make(size.width(), size.height(),
+            kGray_8_SkColorType, kOpaque_SkAlphaType);
     return SkNEW_ARGS(SkWbmpCodec, (info, streamDeleter.detach()));
 }
+
+class SkWbmpScanlineDecoder : public SkScanlineDecoder {
+public:
+    /*
+     * Takes ownership of all pointer paramters.
+     */
+    SkWbmpScanlineDecoder(SkWbmpCodec* codec)
+        : INHERITED(codec->getInfo())
+        , fCodec(codec)
+        , fColorTable(NULL)
+        , fSwizzler(NULL)
+        , fSrcRowBytes(get_src_row_bytes(this->getInfo().width()))
+        , fSrcBuffer(fSrcRowBytes)
+    {}
+
+    SkCodec::Result onGetScanlines(void* dst, int count, size_t dstRowBytes) override {
+        void* dstRow = dst;
+        for (int y = 0; y < count; ++y) {
+            SkCodec::Result rowResult = fCodec->readRow(fSrcBuffer.get(), fSrcRowBytes);
+            if (SkCodec::kSuccess != rowResult) {
+                return rowResult;
+            }
+            fSwizzler->swizzle(dstRow, fSrcBuffer.get());
+            dstRow = SkTAddOffset<void>(dstRow, dstRowBytes);
+        }
+        return SkCodec::kSuccess;
+    }
+
+    SkCodec::Result onStart(const SkImageInfo& dstInfo,
+            const SkCodec::Options& options, SkPMColor inputColorTable[],
+            int* inputColorCount) {
+        if (!fCodec->handleRewind()) {
+            return SkCodec::kCouldNotRewind;
+        }
+        if (options.fSubset) {
+            // Subsets are not supported.
+            return SkCodec::kUnimplemented;
+        }
+        if (dstInfo.dimensions() != this->getInfo().dimensions()) {
+            return SkCodec::kInvalidScale;
+        }
+
+        // Fill in the color table
+        setup_color_table(dstInfo.colorType(), inputColorTable, inputColorCount);
+
+        // Copy the color table to a pointer that can be owned by the scanline decoder
+        if (kIndex_8_SkColorType == dstInfo.colorType()) {
+            fColorTable.reset(SkNEW_ARGS(SkColorTable, (inputColorTable, 2)));
+        }
+
+        // Initialize the swizzler
+        fSwizzler.reset(fCodec->initializeSwizzler(dstInfo,
+                get_color_ptr(fColorTable.get()), options));
+        if (NULL == fSwizzler.get()) {
+            return SkCodec::kInvalidInput;
+        }
+
+        return SkCodec::kSuccess;
+    }
+
+private:
+    SkAutoTDelete<SkWbmpCodec>   fCodec;
+    SkAutoTUnref<SkColorTable>   fColorTable;
+    SkAutoTDelete<SkSwizzler>    fSwizzler;
+    const size_t                 fSrcRowBytes;
+    SkAutoTMalloc<uint8_t>       fSrcBuffer;
+
+    typedef SkScanlineDecoder INHERITED;
+};
+
+SkScanlineDecoder* SkWbmpCodec::NewSDFromStream(SkStream* stream) {
+    SkAutoTDelete<SkWbmpCodec> codec(static_cast<SkWbmpCodec*>(
+            SkWbmpCodec::NewFromStream(stream)));
+    if (!codec) {
+        return NULL;
+    }
+
+    // Return the new scanline decoder
+    return SkNEW_ARGS(SkWbmpScanlineDecoder, (codec.detach()));
+}