Add color space xform support to SkJpegCodec (includes F16!)

src/codec/SkJpegCodec.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 "SkMSAN.h"
 #include "SkJpegCodec.h"
@@ skipping 178 matching lines @@
 }
 
 bool SkJpegCodec::ReadHeader(SkStream* stream, SkCodec** codecOut,
         JpegDecoderMgr** decoderMgrOut) {
 
     // Create a JpegDecoderMgr to own all of the decompress information
     SkAutoTDelete<JpegDecoderMgr> decoderMgr(new JpegDecoderMgr(stream));
 
     // libjpeg errors will be caught and reported here
     if (setjmp(decoderMgr->getJmpBuf())) {
-        return decoderMgr->returnFalse("setjmp");
+        return decoderMgr->returnFalse("ReadHeader");
     }
 
     // Initialize the decompress info and the source manager
     decoderMgr->init();
 
     // Instruct jpeg library to save the markers that we care about.  Since
     // the orientation and color profile will not change, we can skip this
     // step on rewinds.
     if (codecOut) {
         jpeg_save_markers(decoderMgr->dinfo(), kExifMarker, 0xFFFF);
         jpeg_save_markers(decoderMgr->dinfo(), kICCMarker, 0xFFFF);
     }
 
     // Read the jpeg header
     if (JPEG_HEADER_OK != jpeg_read_header(decoderMgr->dinfo(), true)) {
-        return decoderMgr->returnFalse("read_header");
+        return decoderMgr->returnFalse("ReadHeader");
     }
 
     if (codecOut) {
         // Get the encoded color type
         SkEncodedInfo::Color color;
         if (!decoderMgr->getEncodedColor(&color)) {
             return false;
         }
 
         // Create image info object and the codec
@@ skipping 35 matching lines @@
     }
     return nullptr;
 }
 
 SkJpegCodec::SkJpegCodec(int width, int height, const SkEncodedInfo& info, SkStream* stream,
         JpegDecoderMgr* decoderMgr, sk_sp<SkColorSpace> colorSpace, Origin origin,
         sk_sp<SkData> iccData)
     : INHERITED(width, height, info, stream, std::move(colorSpace), origin)
     , fDecoderMgr(decoderMgr)
     , fReadyState(decoderMgr->dinfo()->global_state)
-    , fSrcRow(nullptr)
+    , fSwizzleSrcRow(nullptr)
+    , fColorXformSrcRow(nullptr)
     , fSwizzlerSubset(SkIRect::MakeEmpty())
     , fICCData(std::move(iccData))
 {}
 
 /*
  * Return the row bytes of a particular image type and width
  */
 static size_t get_row_bytes(const j_decompress_ptr dinfo) {
 #ifdef TURBO_HAS_565
     const size_t colorBytes = (dinfo->out_color_space == JCS_RGB565) ? 2 :
@@ skipping 52 matching lines @@
     dinfo.global_state = fReadyState;
     calc_output_dimensions(&dinfo, num, denom);
 
     // Return the calculated output dimensions for the given scale
     return SkISize::Make(dinfo.output_width, dinfo.output_height);
 }
 
 bool SkJpegCodec::onRewind() {
     JpegDecoderMgr* decoderMgr = nullptr;
     if (!ReadHeader(this->stream(), nullptr, &decoderMgr)) {
-        return fDecoderMgr->returnFalse("could not rewind");
+        return fDecoderMgr->returnFalse("onRewind");
     }
     SkASSERT(nullptr != decoderMgr);
     fDecoderMgr.reset(decoderMgr);
 
     fSwizzler.reset(nullptr);
-    fSrcRow = nullptr;
+    fSwizzleSrcRow = nullptr;
+    fColorXformSrcRow = nullptr;
     fStorage.reset();
+    fColorXform.reset(nullptr);
 
     return true;
 }
 
 /*
  * Checks if the conversion between the input image and the requested output
  * image has been implemented
  * Sets the output color space
  */
-bool SkJpegCodec::setOutputColorSpace(const SkImageInfo& dst) {
-    if (kUnknown_SkAlphaType == dst.alphaType()) {
+bool SkJpegCodec::setOutputColorSpace(const SkImageInfo& dstInfo, bool needsColorXform) {
+    if (kUnknown_SkAlphaType == dstInfo.alphaType()) {
         return false;
     }
 
-    if (kOpaque_SkAlphaType != dst.alphaType()) {
+    if (kOpaque_SkAlphaType != dstInfo.alphaType()) {
         SkCodecPrintf("Warning: an opaque image should be decoded as opaque "
                       "- it is being decoded as non-opaque, which will draw slower\n");
     }
 
-    // Check if we will decode to CMYK because a conversion to RGBA is not supported
-    J_COLOR_SPACE colorSpace = fDecoderMgr->dinfo()->jpeg_color_space;
-    bool isCMYK = JCS_CMYK == colorSpace || JCS_YCCK == colorSpace;
+    // Check if we will decode to CMYK.  libjpeg-turbo does not convert CMYK to RGBA, so
+    // we must do it ourselves.
+    J_COLOR_SPACE encodedColorType = fDecoderMgr->dinfo()->jpeg_color_space;
+    bool isCMYK = (JCS_CMYK == encodedColorType || JCS_YCCK == encodedColorType);
 
     // Check for valid color types and set the output color space
-    switch (dst.colorType()) {
+    switch (dstInfo.colorType()) {
         case kRGBA_8888_SkColorType:
             if (isCMYK) {
                 fDecoderMgr->dinfo()->out_color_space = JCS_CMYK;
             } else {
                 fDecoderMgr->dinfo()->out_color_space = JCS_EXT_RGBA;
             }
             return true;
         case kBGRA_8888_SkColorType:
             if (isCMYK) {
                 fDecoderMgr->dinfo()->out_color_space = JCS_CMYK;
+            } else if (needsColorXform) {
+                // Our color transformation code requires RGBA order inputs, but it'll swizzle
+                // to BGRA for us.
+                fDecoderMgr->dinfo()->out_color_space = JCS_EXT_RGBA;
             } else {
                 fDecoderMgr->dinfo()->out_color_space = JCS_EXT_BGRA;
             }
             return true;
         case kRGB_565_SkColorType:
+            if (needsColorXform) {
+                return false;
+            }
+
             if (isCMYK) {
                 fDecoderMgr->dinfo()->out_color_space = JCS_CMYK;
             } else {
 #ifdef TURBO_HAS_565
                 fDecoderMgr->dinfo()->dither_mode = JDITHER_NONE;
                 fDecoderMgr->dinfo()->out_color_space = JCS_RGB565;
 #else
                 fDecoderMgr->dinfo()->out_color_space = JCS_RGB;
 #endif
             }
             return true;
         case kGray_8_SkColorType:
+            if (needsColorXform || JCS_GRAYSCALE != encodedColorType) {
+                return false;
+            }
+
+            fDecoderMgr->dinfo()->out_color_space = JCS_GRAYSCALE;
+            return true;
+        case kRGBA_F16_SkColorType:
+            SkASSERT(needsColorXform);
+
             if (isCMYK) {
-                return false;
+                fDecoderMgr->dinfo()->out_color_space = JCS_CMYK;
             } else {
-                // We will enable decodes to gray even if the image is color because this is
-                // much faster than decoding to color and then converting
-                fDecoderMgr->dinfo()->out_color_space = JCS_GRAYSCALE;
+                fDecoderMgr->dinfo()->out_color_space = JCS_EXT_RGBA;
             }
             return true;
         default:
             return false;
     }
 }
 
 /*
  * Checks if we can natively scale to the requested dimensions and natively scales the
  * dimensions if possible
  */
 bool SkJpegCodec::onDimensionsSupported(const SkISize& size) {
     if (setjmp(fDecoderMgr->getJmpBuf())) {
-        return fDecoderMgr->returnFalse("onDimensionsSupported/setjmp");
+        return fDecoderMgr->returnFalse("onDimensionsSupported");
     }
 
     const unsigned int dstWidth = size.width();
     const unsigned int dstHeight = size.height();
 
     // Set up a fake decompress struct in order to use libjpeg to calculate output dimensions
     // FIXME: Why is this necessary?
     jpeg_decompress_struct dinfo;
     sk_bzero(&dinfo, sizeof(dinfo));
     dinfo.image_width = this->getInfo().width();
@@ skipping 14 matching lines @@
         // Try the next scale
         num -= 1;
         calc_output_dimensions(&dinfo, num, denom);
     }
 
     fDecoderMgr->dinfo()->scale_num = num;
     fDecoderMgr->dinfo()->scale_denom = denom;
     return true;
 }
 
+static bool needs_color_xform(const SkImageInfo& dstInfo, const SkImageInfo& srcInfo) {
+    // FIXME (msarett):
+    // Do a better check for color space equality.
+    return (kRGBA_F16_SkColorType == dstInfo.colorType()) ||
+           (dstInfo.colorSpace() && (dstInfo.colorSpace() != srcInfo.colorSpace()));
+}
+
+int SkJpegCodec::readRows(const SkImageInfo& dstInfo, void* dst, size_t rowBytes, int count) {
+    // Set the jump location for libjpeg-turbo errors
+    if (setjmp(fDecoderMgr->getJmpBuf())) {
+        return 0;
+    }
+
+    // When fSwizzleSrcRow is non-null, it means that we need to swizzle.  In this case,
+    // we will always decode into fSwizzlerSrcRow before swizzling into the next buffer.
+    // We can never swizzle "in place" because the swizzler may perform sampling and/or
+    // subsetting.
+    // When fColorXformSrcRow is non-null, it means that we need to color xform and that
+    // we cannot color xform "in place" (many times we can, but not when the dst is F16).
+    // In this case, we will color xform from fColorXformSrc into the dst.
+    JSAMPLE* decodeDst = (JSAMPLE*) dst;
+    uint32_t* swizzleDst = (uint32_t*) dst;
+    size_t decodeDstRowBytes = rowBytes;
+    size_t swizzleDstRowBytes = rowBytes;
+    if (fSwizzleSrcRow && fColorXformSrcRow) {
+        decodeDst = (JSAMPLE*) fSwizzleSrcRow;
+        swizzleDst = fColorXformSrcRow;
+        decodeDstRowBytes = 0;
+        swizzleDstRowBytes = 0;
+    } else if (fColorXformSrcRow) {
+        decodeDst = (JSAMPLE*) fColorXformSrcRow;
+        swizzleDst = fColorXformSrcRow;
+        decodeDstRowBytes = 0;
+        swizzleDstRowBytes = 0;
+    } else if (fSwizzleSrcRow) {
+        decodeDst = (JSAMPLE*) fSwizzleSrcRow;
+        decodeDstRowBytes = 0;
+    }
+
+    for (int y = 0; y < count; y++) {
+        uint32_t lines = jpeg_read_scanlines(fDecoderMgr->dinfo(), &decodeDst, 1);
+        size_t srcRowBytes = get_row_bytes(fDecoderMgr->dinfo());
+        sk_msan_mark_initialized(decodeDst, decodeDst + srcRowBytes, "skbug.com/4550");
+        if (0 == lines) {
+            return y;
+        }
+
+        if (fSwizzler) {
+            fSwizzler->swizzle(swizzleDst, decodeDst);
+        }
+
+        if (fColorXform) {
+            int width = dstInfo.width();
+            switch (dstInfo.colorType()) {
+                case kRGBA_8888_SkColorType:
+                    fColorXform->applyToRGBA((uint32_t*) dst, swizzleDst, width);
+                    break;
+                case kBGRA_8888_SkColorType:
+                    fColorXform->applyToBGRA((uint32_t*) dst, swizzleDst, width);
+                    break;
+                case kRGBA_F16_SkColorType:
+                    fColorXform->applyToF16((uint64_t*) dst, swizzleDst, width);
+                    break;
+                default:
+                    SkASSERT(false);
+                    break;
+            }
+
+            dst = SkTAddOffset<void>(dst, rowBytes);
+        }
+
+        decodeDst = SkTAddOffset<JSAMPLE>(decodeDst, decodeDstRowBytes);
+        swizzleDst = SkTAddOffset<uint32_t>(swizzleDst, swizzleDstRowBytes);
+    }
+
+    return count;
+}
+
 /*
  * Performs the jpeg decode
  */
 SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
                                          void* dst, size_t dstRowBytes,
                                          const Options& options, SkPMColor*, int*,
                                          int* rowsDecoded) {
     if (options.fSubset) {
         // Subsets are not supported.
         return kUnimplemented;
     }
 
     // Get a pointer to the decompress info since we will use it quite frequently
     jpeg_decompress_struct* dinfo = fDecoderMgr->dinfo();
 
     // Set the jump location for libjpeg errors
     if (setjmp(fDecoderMgr->getJmpBuf())) {
         return fDecoderMgr->returnFailure("setjmp", kInvalidInput);
     }
 
     // Check if we can decode to the requested destination and set the output color space
-    if (!this->setOutputColorSpace(dstInfo)) {
-        return fDecoderMgr->returnFailure("conversion_possible", kInvalidConversion);
+    bool needsColorXform = needs_color_xform(dstInfo, this->getInfo());
+    if (!this->setOutputColorSpace(dstInfo, needsColorXform)) {
+        return fDecoderMgr->returnFailure("setOutputColorSpace", kInvalidConversion);
     }
 
-    // Now, given valid output dimensions, we can start the decompress
+    if (!this->initializeColorXform(dstInfo, needsColorXform)) {
+        return fDecoderMgr->returnFailure("initializeColorXform", kInvalidParameters);
+    }
+
     if (!jpeg_start_decompress(dinfo)) {
         return fDecoderMgr->returnFailure("startDecompress", kInvalidInput);
     }
 
     // The recommended output buffer height should always be 1 in high quality modes.
     // If it's not, we want to know because it means our strategy is not optimal.
     SkASSERT(1 == dinfo->rec_outbuf_height);
 
     J_COLOR_SPACE colorSpace = dinfo->out_color_space;
     if (JCS_CMYK == colorSpace || JCS_RGB == colorSpace) {
         this->initializeSwizzler(dstInfo, options);
     }
 
-    // Perform the decode a single row at a time
-    uint32_t dstHeight = dstInfo.height();
+    this->allocateStorage(dstInfo);
 
-    JSAMPLE* dstRow;
-    if (fSwizzler) {
-        // write data to storage row, then sample using swizzler
-        dstRow = fSrcRow;
-    } else {
-        // write data directly to dst
-        dstRow = (JSAMPLE*) dst;
-    }
-
-    for (uint32_t y = 0; y < dstHeight; y++) {
-        // Read rows of the image
-        uint32_t lines = jpeg_read_scanlines(dinfo, &dstRow, 1);
-        sk_msan_mark_initialized(dstRow, dstRow + dstRowBytes, "skbug.com/4550");
-
-        // If we cannot read enough rows, assume the input is incomplete
-        if (lines != 1) {
-            *rowsDecoded = y;
-            return fDecoderMgr->returnFailure("Incomplete image data", kIncompleteInput);
-        }
-
-        if (fSwizzler) {
-            // use swizzler to sample row
-            fSwizzler->swizzle(dst, dstRow);
-            dst = SkTAddOffset<JSAMPLE>(dst, dstRowBytes);
-        } else {
-            dstRow = SkTAddOffset<JSAMPLE>(dstRow, dstRowBytes);
-        }
+    int rows = this->readRows(dstInfo, dst, dstRowBytes, dstInfo.height());
+    if (rows < dstInfo.height()) {
+        *rowsDecoded = rows;
+        return fDecoderMgr->returnFailure("Incomplete image data", kIncompleteInput);
     }
 
     return kSuccess;
 }
 
+void SkJpegCodec::allocateStorage(const SkImageInfo& dstInfo) {
+    size_t swizzleBytes = 0;
+    if (fSwizzler) {
+        swizzleBytes = get_row_bytes(fDecoderMgr->dinfo());
+        SkASSERT(!fColorXform || SkIsAlign4(swizzleBytes));
+    }
+
+    size_t xformBytes = 0;
+    if (kRGBA_F16_SkColorType == dstInfo.colorType()) {
+        SkASSERT(fColorXform);
+        xformBytes = dstInfo.width() * sizeof(SkColorSpaceXform::RGBA32);
+    }
+
+    size_t totalBytes = swizzleBytes + xformBytes;
+    if (totalBytes > 0) {
+        fStorage.reset(totalBytes);
+        fSwizzleSrcRow = (swizzleBytes > 0) ? fStorage.get() : nullptr;
+        fColorXformSrcRow = (xformBytes > 0) ?
+                SkTAddOffset<uint32_t>(fStorage.get(), swizzleBytes) : nullptr;
+    }
+}
+
 void SkJpegCodec::initializeSwizzler(const SkImageInfo& dstInfo, const Options& options) {
     // libjpeg-turbo may have already performed color conversion.  We must indicate the
     // appropriate format to the swizzler.
     SkEncodedInfo swizzlerInfo = this->getEncodedInfo();
     bool preSwizzled = true;
     switch (fDecoderMgr->dinfo()->out_color_space) {
         case JCS_RGB:
             preSwizzled = false;
             swizzlerInfo = SkEncodedInfo::Make(SkEncodedInfo::kRGB_Color,
                                                swizzlerInfo.alpha(),
                                                swizzlerInfo.bitsPerComponent());
             break;
         case JCS_CMYK:
             preSwizzled = false;
-            swizzlerInfo = SkEncodedInfo::Make(
-                    SkEncodedInfo::kInvertedCMYK_Color, swizzlerInfo.alpha(),
-                    swizzlerInfo.bitsPerComponent());
+            swizzlerInfo = SkEncodedInfo::Make(SkEncodedInfo::kInvertedCMYK_Color,
+                                               swizzlerInfo.alpha(),
+                                               swizzlerInfo.bitsPerComponent());
             break;
         default:
             break;
     }
 
     Options swizzlerOptions = options;
     if (options.fSubset) {
         // Use fSwizzlerSubset if this is a subset decode.  This is necessary in the case
         // where libjpeg-turbo provides a subset and then we need to subset it further.
         // Also, verify that fSwizzlerSubset is initialized and valid.
         SkASSERT(!fSwizzlerSubset.isEmpty() && fSwizzlerSubset.x() <= options.fSubset->x() &&
                 fSwizzlerSubset.width() == options.fSubset->width());
         swizzlerOptions.fSubset = &fSwizzlerSubset;
     }
     fSwizzler.reset(SkSwizzler::CreateSwizzler(swizzlerInfo, nullptr, dstInfo, swizzlerOptions,
                                                nullptr, preSwizzled));
     SkASSERT(fSwizzler);
-    fStorage.reset(get_row_bytes(fDecoderMgr->dinfo()));
-    fSrcRow = fStorage.get();
+}
+
+bool SkJpegCodec::initializeColorXform(const SkImageInfo& dstInfo, bool needsColorXform) {
+    if (needsColorXform) {
+        fColorXform = SkColorSpaceXform::New(sk_ref_sp(this->getInfo().colorSpace()),
+                                             sk_ref_sp(dstInfo.colorSpace()));
+        if (!fColorXform && kRGBA_F16_SkColorType == dstInfo.colorType()) {
+            return false;
+        }
+    }
+
+    return true;
 }
 
 SkSampler* SkJpegCodec::getSampler(bool createIfNecessary) {
     if (!createIfNecessary || fSwizzler) {
-        SkASSERT(!fSwizzler || (fSrcRow && fStorage.get() == fSrcRow));
+        SkASSERT(!fSwizzler || (fSwizzleSrcRow && fStorage.get() == fSwizzleSrcRow));
         return fSwizzler;
     }
 
     this->initializeSwizzler(this->dstInfo(), this->options());
+    this->allocateStorage(this->dstInfo());
     return fSwizzler;
 }
 
 SkCodec::Result SkJpegCodec::onStartScanlineDecode(const SkImageInfo& dstInfo,
         const Options& options, SkPMColor ctable[], int* ctableCount) {
     // Set the jump location for libjpeg errors
     if (setjmp(fDecoderMgr->getJmpBuf())) {
         SkCodecPrintf("setjmp: Error from libjpeg\n");
         return kInvalidInput;
     }
 
     // Check if we can decode to the requested destination and set the output color space
-    if (!this->setOutputColorSpace(dstInfo)) {
+    bool needsColorXform = needs_color_xform(dstInfo, this->getInfo());
+    if (!this->setOutputColorSpace(dstInfo, needsColorXform)) {
         return kInvalidConversion;
     }
 
-    // Now, given valid output dimensions, we can start the decompress
+    if (!this->initializeColorXform(dstInfo, needsColorXform)) {
+        return fDecoderMgr->returnFailure("initializeColorXform", kInvalidParameters);
+    }
+
     if (!jpeg_start_decompress(fDecoderMgr->dinfo())) {
         SkCodecPrintf("start decompress failed\n");
         return kInvalidInput;
     }
 
 #ifdef TURBO_HAS_CROP
     if (options.fSubset) {
         uint32_t startX = options.fSubset->x();
         uint32_t width = options.fSubset->width();
 
@@ skipping 40 matching lines @@
     }
 
     // We will need a swizzler if we are performing a subset decode or
     // converting from CMYK.
     J_COLOR_SPACE colorSpace = fDecoderMgr->dinfo()->out_color_space;
     if (options.fSubset || JCS_CMYK == colorSpace || JCS_RGB == colorSpace) {
         this->initializeSwizzler(dstInfo, options);
     }
 #endif
 
+    this->allocateStorage(dstInfo);
+
     return kSuccess;
 }
 
 int SkJpegCodec::onGetScanlines(void* dst, int count, size_t dstRowBytes) {
-    // Set the jump location for libjpeg errors
-    if (setjmp(fDecoderMgr->getJmpBuf())) {
-        return fDecoderMgr->returnFailure("setjmp", kInvalidInput);
-    }
-    // Read rows one at a time
-    JSAMPLE* dstRow;
-    size_t srcRowBytes = get_row_bytes(fDecoderMgr->dinfo());
-    if (fSwizzler) {
-        // write data to storage row, then sample using swizzler
-        dstRow = fSrcRow;
-    } else {
-        // write data directly to dst
-        SkASSERT(count == 1 || dstRowBytes >= srcRowBytes);
-        dstRow = (JSAMPLE*) dst;
+    int rows = this->readRows(this->dstInfo(), dst, dstRowBytes, count);
+    if (rows < count) {
+        // This allows us to skip calling jpeg_finish_decompress().
+        fDecoderMgr->dinfo()->output_scanline = this->dstInfo().height();
     }
 
-    for (int y = 0; y < count; y++) {
-        // Read row of the image
-        uint32_t rowsDecoded = jpeg_read_scanlines(fDecoderMgr->dinfo(), &dstRow, 1);
-        sk_msan_mark_initialized(dstRow, dstRow + srcRowBytes, "skbug.com/4550");
-        if (rowsDecoded != 1) {
-            fDecoderMgr->dinfo()->output_scanline = this->dstInfo().height();
-            return y;
-        }
-
-        if (fSwizzler) {
-            // use swizzler to sample row
-            fSwizzler->swizzle(dst, dstRow);
-            dst = SkTAddOffset<JSAMPLE>(dst, dstRowBytes);
-        } else {
-            dstRow = SkTAddOffset<JSAMPLE>(dstRow, dstRowBytes);
-        }
-    }
-    return count;
+    return rows;
 }
 
 bool SkJpegCodec::onSkipScanlines(int count) {
     // Set the jump location for libjpeg errors
     if (setjmp(fDecoderMgr->getJmpBuf())) {
-        return fDecoderMgr->returnFalse("setjmp");
+        return fDecoderMgr->returnFalse("onSkipScanlines");
     }
 
 #ifdef TURBO_HAS_SKIP
     return (uint32_t) count == jpeg_skip_scanlines(fDecoderMgr->dinfo(), count);
 #else
-    if (!fSrcRow) {
+    if (!fSwizzleSrcRow) {
         fStorage.reset(get_row_bytes(fDecoderMgr->dinfo()));
-        fSrcRow = fStorage.get();
+        fSwizzleSrcRow = fStorage.get();
     }
 
     for (int y = 0; y < count; y++) {
-        if (1 != jpeg_read_scanlines(fDecoderMgr->dinfo(), &fSrcRow, 1)) {
+        if (1 != jpeg_read_scanlines(fDecoderMgr->dinfo(), &fSwizzleSrcRow, 1)) {
             return false;
         }
     }
     return true;
 #endif
 }
 
 static bool is_yuv_supported(jpeg_decompress_struct* dinfo) {
     // Scaling is not supported in raw data mode.
     SkASSERT(dinfo->scale_num == dinfo->scale_denom);
@@ skipping 184 matching lines @@
 
         JDIMENSION linesRead = jpeg_read_raw_data(dinfo, yuv, numRowsPerBlock);
         if (linesRead < remainingRows) {
             // FIXME: Handle incomplete YUV decodes without signalling an error.
             return kInvalidInput;
         }
     }
 
     return kSuccess;
 }