Fill incomplete images in SkCodec parent class

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"
@@ skipping 20 matching lines @@
     , 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) {
+                                           int* inputColorCount,
+                                           int* rowsDecoded) {
     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;
     }
 
     Result result = this->prepareToDecode(dstInfo, opts, inputColorPtr, inputColorCount);
     if (kSuccess != result) {
         return result;
     }
 
     // Perform the decode
-    return this->decodeRows(dstInfo, dst, dstRowBytes, opts);
+    uint32_t rows = this->decodeRows(dstInfo, dst, dstRowBytes, opts);
+    if (rows != dstInfo.height()) {
+        // We set rowsDecoded equal to the height because the background has already
+        // been filled.  RLE encodings sometimes skip pixels, so we always start by
+        // filling the background.
+        *rowsDecoded = dstInfo.height();
+        return kIncompleteInput;
+    }
 }
 
 /*
  * 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 199 matching lines @@
 
     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::decodeRows(const SkImageInfo& dstInfo,
-                                          void* dst, size_t dstRowBytes,
-                                          const Options& opts) {
+uint32_t 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 = 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());
-    SkSwizzler::Fill(dst, dstInfo, dstRowBytes, height, SK_ColorTRANSPARENT,
-            NULL, opts.fZeroInitialized);
+    SkSwizzler::Fill(dst, dstInfo, dstRowBytes, SK_ColorTRANSPARENT, 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
+            // It would be better to check for the EOF marker before indicating
             // success, but we may be performing a scanline decode, which
-            // may require us to stop before decoding the full height.
-            return kSuccess;
+            // would require us to stop before decoding the full height.
+            return height;
         }
 
         // Every entry takes at least two bytes
         if ((int) fRLEBytes - fCurrRLEByte < 2) {
             SkCodecPrintf("Warning: might be incomplete RLE input.\n");
             if (this->checkForMoreData() < 2) {
-                return kIncompleteInput;
+                return y;
             }
         }
 
         // Read the next two bytes.  These bytes have different meanings
         // depending on their values.  In the first interpretation, the first
         // byte is an escape flag and the second byte indicates what special
         // task to perform.
         const uint8_t flag = fStreamBuffer.get()[fCurrRLEByte++];
         const uint8_t task = fStreamBuffer.get()[fCurrRLEByte++];
 
         // Perform decoding
         if (RLE_ESCAPE == flag) {
             switch (task) {
                 case RLE_EOL:
                     x = 0;
                     y++;
                     break;
                 case RLE_EOF:
                     return kSuccess;
                 case RLE_DELTA: {
                     // Two bytes are needed to specify delta
                     if ((int) fRLEBytes - fCurrRLEByte < 2) {
                         SkCodecPrintf("Warning: might be incomplete RLE input.\n");
                         if (this->checkForMoreData() < 2) {
-                            return kIncompleteInput;
+                            return y;
                         }
                     }
                     // Modify x and y
                     const uint8_t dx = fStreamBuffer.get()[fCurrRLEByte++];
                     const uint8_t dy = fStreamBuffer.get()[fCurrRLEByte++];
                     x += dx;
                     y += dy;
                     if (x > width || y > height) {
                         SkCodecPrintf("Warning: invalid RLE input.\n");
-                        return kInvalidInput;
+                        return y - dy;
                     }
                     break;
                 }
                 default: {
                     // If task does not match any of the above signals, it
                     // indicates that we have a sequence of non-RLE pixels.
                     // Furthermore, the value of task is equal to the number
                     // of pixels to interpret.
                     uint8_t numPixels = task;
                     const size_t rowBytes = compute_row_bytes(numPixels,
                             this->bitsPerPixel());
                     // Abort if setting numPixels moves us off the edge of the
                     // image.
                     if (x + numPixels > width) {
                         SkCodecPrintf("Warning: invalid RLE input.\n");
-                        return kInvalidInput;
+                        return y;
                     }
                     // Also abort if there are not enough bytes
                     // remaining in the stream to set numPixels.
                     if ((int) fRLEBytes - fCurrRLEByte < SkAlign2(rowBytes)) {
                         SkCodecPrintf("Warning: might be incomplete RLE input.\n");
                         if (this->checkForMoreData() < SkAlign2(rowBytes)) {
-                            return kIncompleteInput;
+                            return y;
                         }
                     }
                     // Set numPixels number of pixels
                     while (numPixels > 0) {
                         switch(this->bitsPerPixel()) {
                             case 4: {
                                 SkASSERT(fCurrRLEByte < fRLEBytes);
                                 uint8_t val = fStreamBuffer.get()[fCurrRLEByte++];
                                 setPixel(dst, dstRowBytes, dstInfo, x++,
                                         y, val >> 4);
@@ skipping 15 matching lines @@
                                 SkASSERT(fCurrRLEByte + 2 < fRLEBytes);
                                 uint8_t blue = fStreamBuffer.get()[fCurrRLEByte++];
                                 uint8_t green = fStreamBuffer.get()[fCurrRLEByte++];
                                 uint8_t red = fStreamBuffer.get()[fCurrRLEByte++];
                                 setRGBPixel(dst, dstRowBytes, dstInfo,
                                             x++, y, red, green, blue);
                                 numPixels--;
                             }
                             default:
                                 SkASSERT(false);
-                                return kInvalidInput;
+                                return y;
                         }
                     }
                     // Skip a byte if necessary to maintain alignment
                     if (!SkIsAlign2(rowBytes)) {
                         fCurrRLEByte++;
                     }
                     break;
                 }
             }
         } else {
             // If the first byte read is not a flag, it indicates the number of
             // pixels to set in RLE mode.
             const uint8_t numPixels = flag;
             const int endX = SkTMin<int>(x + numPixels, width);
 
             if (24 == this->bitsPerPixel()) {
                 // In RLE24, the second byte read is part of the pixel color.
                 // There are two more required bytes to finish encoding the
                 // color.
                 if ((int) fRLEBytes - fCurrRLEByte < 2) {
                     SkCodecPrintf("Warning: might be incomplete RLE input.\n");
                     if (this->checkForMoreData() < 2) {
-                        return kIncompleteInput;
+                        return y;
                     }
                 }
 
                 // Fill the pixels up to endX with the specified color
                 uint8_t blue = task;
                 uint8_t green = fStreamBuffer.get()[fCurrRLEByte++];
                 uint8_t red = fStreamBuffer.get()[fCurrRLEByte++];
                 while (x < endX) {
                     setRGBPixel(dst, dstRowBytes, dstInfo, x++, y, red, green, blue);
                 }
@@ skipping 11 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;
                 }
             }
         }
     }
 }