Scanline decoding for bmp

src/codec/SkBmpRLECodec.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 "SkBmpRLECodec.h"
 #include "SkCodecPriv.h"
 #include "SkColorPriv.h"
+#include "SkScaledCodec.h"
 #include "SkScanlineDecoder.h"
 #include "SkStream.h"
 
 /*
  * Creates an instance of the decoder
  * Called only by NewFromStream
  */
 SkBmpRLECodec::SkBmpRLECodec(const SkImageInfo& info, SkStream* stream,
                              uint16_t bitsPerPixel, uint32_t numColors,
                              uint32_t bytesPerColor, uint32_t offset,
                              SkBmpCodec::RowOrder rowOrder, size_t RLEBytes)
     : INHERITED(info, stream, bitsPerPixel, rowOrder)
     , fColorTable(NULL)
     , fNumColors(this->computeNumColors(numColors))
     , fBytesPerColor(bytesPerColor)
     , fOffset(offset)
     , fStreamBuffer(SkNEW_ARRAY(uint8_t, RLEBytes))
     , fRLEBytes(RLEBytes)
     , fCurrRLEByte(0)
+    , fSampleX(1)
 {}
 
 /*
  * Initiates the bitmap decode
  */
 SkCodec::Result SkBmpRLECodec::onGetPixels(const SkImageInfo& dstInfo,
-                                        void* dst, size_t dstRowBytes,
-                                        const Options& opts,
-                                        SkPMColor* inputColorPtr,
-                                        int* inputColorCount) {
+                                           void* dst, size_t dstRowBytes,
+                                           const Options& opts,
+                                           SkPMColor* inputColorPtr,
+                                           int* inputColorCount) {
     if (!this->rewindIfNeeded()) {
         return kCouldNotRewind;
     }
     if (opts.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }
     if (dstInfo.dimensions() != this->getInfo().dimensions()) {
         SkCodecPrintf("Error: scaling not supported.\n");
         return kInvalidScale;
     }
     if (!conversion_possible(dstInfo, this->getInfo())) {
         SkCodecPrintf("Error: cannot convert input type to output type.\n");
         return kInvalidConversion;
     }
 
-    // Create the color table if necessary and prepare the stream for decode
-    // Note that if it is non-NULL, inputColorCount will be modified
-    if (!this->createColorTable(inputColorCount)) {
-        SkCodecPrintf("Error: could not create color table.\n");
-        return kInvalidInput;
-    }
-
-    // Copy the color table to the client if necessary
-    copy_color_table(dstInfo, fColorTable, inputColorPtr, inputColorCount);
-
-    // Initialize a swizzler if necessary
-    if (!this->initializeStreamBuffer()) {
-        SkCodecPrintf("Error: cannot initialize swizzler.\n");
-        return kInvalidConversion;
+    Result result = this->prepareToDecode(dstInfo, opts, inputColorPtr, inputColorCount);
+    if (kSuccess != result) {
+        return result;
     }
 
     // Perform the decode
-    return decode(dstInfo, dst, dstRowBytes, opts);
+    return this->decodeRows(dstInfo, dst, dstRowBytes, opts);
 }
 
 /*
  * Process the color table for the bmp input
  */
  bool SkBmpRLECodec::createColorTable(int* numColors) {
     // Allocate memory for color table
     uint32_t colorBytes = 0;
     SkPMColor colorTable[256];
     if (this->bitsPerPixel() <= 8) {
@@ skipping 50 matching lines @@
         SkCodecPrintf("Error: unable to skip to image data.\n");
         return false;
     }
 
     // Return true on success
     return true;
 }
 
 bool SkBmpRLECodec::initializeStreamBuffer() {
     // Setup a buffer to contain the full input stream
+    // TODO (msarett): I'm not sure it is smart or optimal to trust fRLEBytes (read from header)

[scroggo, 2015/08/27 20:14:23]

FWIW, we could use a constant buffer size, like we do for JPEG, and fill it when
necessary.

Or we could only read whatever we think we need for the current calculations.

[msarett, 2015/08/27 21:21:46]

Yeah I think both of those are good candidates.

+    //                 as the size of our buffer.  First of all, the decode fails if fRLEBytes is
+    //                 corrupt (negative, zero, or small) when we might be able to decode
+    //                 successfully with a fixed size buffer.  Additionally, we would save memory
+    //                 using a fixed size buffer if the RLE encoding is large.  On the other hand,
+    //                 we may also waste memory with a fixed size buffer.  And determining a
+    //                 minimum size for our buffer would depend on the image width (so it's not
+    //                 really "fixed" size), and we may end up allocating a buffer that is
+    //                 generally larger than the average encoded size anyway.
     size_t totalBytes = this->stream()->read(fStreamBuffer.get(), fRLEBytes);
     if (totalBytes < fRLEBytes) {
         fRLEBytes = totalBytes;
         SkCodecPrintf("Warning: incomplete RLE file.\n");
     }
     if (fRLEBytes == 0) {
         SkCodecPrintf("Error: could not read RLE image data.\n");
         return false;
     }
     return true;
@@ skipping 33 matching lines @@
     fRLEBytes = remainingBytes + additionalBytes;
     return fRLEBytes;
 }
 
 /*
  * Set an RLE pixel using the color table
  */
 void SkBmpRLECodec::setPixel(void* dst, size_t dstRowBytes,
                              const SkImageInfo& dstInfo, uint32_t x, uint32_t y,
                              uint8_t index) {
-    // Set the row
-    int height = dstInfo.height();
-    int row;
-    if (SkBmpCodec::kBottomUp_RowOrder == this->rowOrder()) {
-        row = height - y - 1;
-    } else {
-        row = y;
-    }
+    if (SkScaledCodec::IsCoordNecessary(x, fSampleX, dstInfo.width())) {
+        // Set the row
+        uint32_t row = this->getDstRow(y, dstInfo.height());
 
-    // Set the pixel based on destination color type
-    switch (dstInfo.colorType()) {
-        case kN32_SkColorType: {
-            SkPMColor* dstRow = SkTAddOffset<SkPMColor>((SkPMColor*) dst,
-                    row * (int) dstRowBytes);
-            dstRow[x] = fColorTable->operator[](index);
-            break;
+        // Set the pixel based on destination color type
+        switch (dstInfo.colorType()) {
+            case kN32_SkColorType: {
+                SkPMColor* dstRow = SkTAddOffset<SkPMColor>((SkPMColor*) dst,
+                        row * (int) dstRowBytes);
+                dstRow[SkScaledCodec::GetDstCoord(x, fSampleX)] =
+                        fColorTable->operator[](index);
+                break;
+            }
+            case kRGB_565_SkColorType: {
+                uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
+                dstRow[SkScaledCodec::GetDstCoord(x, fSampleX)] =
+                        SkPixel32ToPixel16(fColorTable->operator[](index));
+                break;
+            }
+            default:
+                // This case should not be reached.  We should catch an invalid
+                // color type when we check that the conversion is possible.
+                SkASSERT(false);
+                break;
         }
-        case kRGB_565_SkColorType: {
-            uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
-            dstRow[x] = SkPixel32ToPixel16(fColorTable->operator[](index));
-            break;
-        }
-        default:
-            // This case should not be reached.  We should catch an invalid
-            // color type when we check that the conversion is possible.
-            SkASSERT(false);
-            break;
     }
 }
 
 /*
  * Set an RLE pixel from R, G, B values
  */
 void SkBmpRLECodec::setRGBPixel(void* dst, size_t dstRowBytes,
                                 const SkImageInfo& dstInfo, uint32_t x,
                                 uint32_t y, uint8_t red, uint8_t green,
                                 uint8_t blue) {
-    // Set the row
-    int height = dstInfo.height();
-    int row;
-    if (SkBmpCodec::kBottomUp_RowOrder == this->rowOrder()) {
-        row = height - y - 1;
-    } else {
-        row = y;
+    if (SkScaledCodec::IsCoordNecessary(x, fSampleX, dstInfo.width())) {
+        // Set the row
+        uint32_t row = this->getDstRow(y, dstInfo.height());
+
+        // Set the pixel based on destination color type
+        switch (dstInfo.colorType()) {
+            case kN32_SkColorType: {
+                SkPMColor* dstRow = SkTAddOffset<SkPMColor>((SkPMColor*) dst,
+                        row * (int) dstRowBytes);
+                dstRow[SkScaledCodec::GetDstCoord(x, fSampleX)] =
+                        SkPackARGB32NoCheck(0xFF, red, green, blue);
+                break;
+            }
+            case kRGB_565_SkColorType: {
+                uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
+                dstRow[SkScaledCodec::GetDstCoord(x, fSampleX)] =
+                        SkPack888ToRGB16(red, green, blue);
+                break;
+            }
+            default:
+                // This case should not be reached.  We should catch an invalid
+                // color type when we check that the conversion is possible.
+                SkASSERT(false);
+                break;
+        }
+    }
+}
+
+SkCodec::Result SkBmpRLECodec::prepareToDecode(const SkImageInfo& dstInfo,
+        const SkCodec::Options& options, SkPMColor inputColorPtr[], int* inputColorCount) {
+    // Create the color table if necessary and prepare the stream for decode
+    // Note that if it is non-NULL, inputColorCount will be modified
+    if (!this->createColorTable(inputColorCount)) {
+        SkCodecPrintf("Error: could not create color table.\n");
+        return SkCodec::kInvalidInput;
     }
 
-    // Set the pixel based on destination color type
-    switch (dstInfo.colorType()) {
-        case kN32_SkColorType: {
-            SkPMColor* dstRow = SkTAddOffset<SkPMColor>((SkPMColor*) dst,
-                    row * (int) dstRowBytes);
-            dstRow[x] = SkPackARGB32NoCheck(0xFF, red, green, blue);
-            break;
-        }
-        case kRGB_565_SkColorType: {
-            uint16_t* dstRow = SkTAddOffset<uint16_t>(dst, row * (int) dstRowBytes);
-            dstRow[x] = SkPack888ToRGB16(red, green, blue);
-            break;
-        }
-        default:
-            // This case should not be reached.  We should catch an invalid
-            // color type when we check that the conversion is possible.
-            SkASSERT(false);
-            break;
+    // Copy the color table to the client if necessary
+    copy_color_table(dstInfo, this->fColorTable, inputColorPtr, inputColorCount);
+
+    // Initialize a buffer for encoded RLE data
+    if (!this->initializeStreamBuffer()) {
+        SkCodecPrintf("Error: cannot initialize stream buffer.\n");
+        return SkCodec::kInvalidConversion;
     }
+
+    fCurrRLEByte = 0;
+    SkScaledCodec::ComputeSampleSize(dstInfo, this->getInfo(), &fSampleX, NULL);
+
+    return SkCodec::kSuccess;
 }
 
 /*
  * Performs the bitmap decoding for RLE input format
  * RLE decoding is performed all at once, rather than a one row at a time
  */
-SkCodec::Result SkBmpRLECodec::decode(const SkImageInfo& dstInfo,
-                                      void* dst, size_t dstRowBytes,
-                                      const Options& opts) {
+SkCodec::Result SkBmpRLECodec::decodeRows(const SkImageInfo& dstInfo,
+                                          void* dst, size_t dstRowBytes,
+                                          const Options& opts) {
     // Set RLE flags
     static const uint8_t RLE_ESCAPE = 0;
     static const uint8_t RLE_EOL = 0;
     static const uint8_t RLE_EOF = 1;
     static const uint8_t RLE_DELTA = 2;
 
     // Set constant values
-    const int width = dstInfo.width();
+    const int width = this->getInfo().width();
     const int height = dstInfo.height();
 
     // Destination parameters
     int x = 0;
     int y = 0;
 
     // Set the background as transparent.  Then, if the RLE code skips pixels,
     // the skipped pixels will be transparent.
     // Because of the need for transparent pixels, kN32 is the only color
     // type that makes sense for the destination format.
     SkASSERT(kN32_SkColorType == dstInfo.colorType());
-    if (kNo_ZeroInitialized == opts.fZeroInitialized) {
-        SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, SK_ColorTRANSPARENT, NULL);
-    }
+    SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, SK_ColorTRANSPARENT,
+            NULL, opts.fZeroInitialized);
 
     while (true) {
         // If we have reached a row that is beyond the requested height, we have
         // succeeded.
         if (y >= height) {
             // It would be better to check for the EOF marker before returning
             // success, but we may be performing a scanline decode, which
             // may require us to stop before decoding the full height.
             return kSuccess;
         }
@@ skipping 146 matching lines @@
                 // Set the indicated number of pixels
                 for (int which = 0; x < endX; x++) {
                     setPixel(dst, dstRowBytes, dstInfo, x, y,
                             indices[which]);
                     which = !which;
                 }
             }
         }
     }
 }