SkJpegCodec

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
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+/*
+ * 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 "SkJpegCodec.h"
+#include "SkJpegDecoderMgr.h"
+#include "SkJpegUtility.h"
+#include "SkCodecPriv.h"
+#include "SkColorPriv.h"
+#include "SkStream.h"
+#include "SkTemplates.h"
+#include "SkTypes.h"
+
+// stdio is needed for jpeglib
+#include <stdio.h>
+
+extern "C" {
+    #include "jerror.h"
+    #include "jmorecfg.h"
+    #include "jpegint.h"
+    #include "jpeglib.h"
+}
+
+// ANDROID_RGB
+// If this is defined in the jpeg headers it indicates that jpeg offers
+// support for two additional formats: JCS_RGBA_8888 and JCS_RGB_565.
+
+/*
+ * Get the source configuarion for the swizzler
+ */
+SkSwizzler::SrcConfig get_src_config(jpeg_decompress_struct* dinfo) {

[scroggo, 2015/04/15 00:31:06]

Do we modify dinfo? Could it be const& instead?

[msarett, 2015/04/15 12:43:11]

Done.

+    if (JCS_CMYK == dinfo->out_color_space) {
+        // We will need to perform a manual conversion
+        return  SkSwizzler::kRGBX;
+    }
+    if (3 == dinfo->out_color_components && JCS_RGB == dinfo->out_color_space) {
+        return SkSwizzler::kRGB;
+    }
+#ifdef ANDROID_RGB
+    if (JCS_RGBA_8888 == dinfo->out_color_space) {
+        return SkSwizzler::kRGBX;
+    }
+
+    if (JCS_RGB_565 == dinfo->out_color_space) {
+        return SkSwizzler::kRGB_565;
+    }
+#endif
+    if (1 == dinfo->out_color_components && JCS_GRAYSCALE == dinfo->out_color_space) {
+        return SkSwizzler::kGray;
+    }
+    return SkSwizzler::kUnknown;
+}
+
+/*
+ * Convert a row of CMYK samples to RGBX in place.
+ * Note that this method moves the row pointer.
+ * @param width the number of pixels in the row that is being converted
+ *              CMYK is stored as four bytes per pixel
+ */
+static void convert_CMYK_to_RGB(uint8_t* row, uint32_t width) {
+    // We will implement a crude conversion from CMYK -> RGB using formulas
+    // from easyrgb.com.
+    //
+    // CMYK -> CMY
+    // C = C * (1 - K) + K
+    // M = M * (1 - K) + K
+    // Y = Y * (1 - K) + K
+    //
+    // libjpeg actually gives us inverted CMYK, so we must subtract the
+    // original terms from 1.
+    // CMYK -> CMY
+    // C = (1 - C) * (1 - (1 - K)) + (1 - K)
+    // M = (1 - M) * (1 - (1 - K)) + (1 - K)
+    // Y = (1 - Y) * (1 - (1 - K)) + (1 - K)
+    //
+    // Simplifying the above expression.
+    // CMYK -> CMY
+    // C = 1 - CK
+    // M = 1 - MK
+    // Y = 1 - YK
+    //
+    // CMY -> RGB
+    // R = (1 - C) * 255
+    // G = (1 - M) * 255
+    // B = (1 - Y) * 255
+    //
+    // Therefore the full conversion is below.  This can be verified at
+    // www.rapidtables.com (assuming inverted CMYK).
+    // CMYK -> RGB
+    // R = C * K * 255
+    // G = M * K * 255
+    // B = Y * K * 255
+    //
+    // As a final note, we have treated the CMYK values as if they were on
+    // a scale from 0-1, when in fact they are 8-bit ints scaling from 0-255.
+    // We must divide each CMYK component by 255 to obtain the true conversion
+    // we should perform.
+    // CMYK -> RGB
+    // R = C * K / 255
+    // G = M * K / 255
+    // B = Y * K / 255
+    for (uint32_t x = 0; x < width; x++, row += 4) {
+        row[0] = SkMulDiv255Round(row[0], row[3]);
+        row[1] = SkMulDiv255Round(row[1], row[3]);
+        row[2] = SkMulDiv255Round(row[2], row[3]);
+        row[3] = 0xFF;
+    }
+}
+
+bool SkJpegCodec::IsJpeg(SkStream* stream) {
+    static const uint8_t jpegSig[] = { 0xFF, 0xD8, 0xFF };
+    char buffer[sizeof(jpegSig)];
+    return stream->read(buffer, sizeof(jpegSig)) == sizeof(jpegSig) &&
+            !memcmp(buffer, jpegSig, sizeof(jpegSig));
+}
+
+bool SkJpegCodec::ReadHeader(SkStream* stream, SkCodec** codecOut,
+        JpegDecoderMgr** decoderMgrOut) {
+
+    // Create a JpegDecoderMgr to own all of the decompress information
+    SkAutoTDelete<JpegDecoderMgr> decoderMgr(SkNEW_ARGS(JpegDecoderMgr, (stream)));
+
+    // libjpeg errors will be caught and reported here
+    if (setjmp(decoderMgr->errorMgr()->fJmpBuf)) {
+        return decoderMgr->returnFalse("setjmp");
+    }
+
+    // Initialize the decompress info and the source manager
+    decoderMgr->init();
+
+    // Read the jpeg header
+    if (JPEG_HEADER_OK != jpeg_read_header(decoderMgr->dinfo(), true)) {
+        return decoderMgr->returnFalse("read_header");
+    }
+
+    if (NULL != codecOut) {
+        // Recommend the color type to decode to
+        const SkColorType colorType = decoderMgr->getColorType();
+
+        // Create image info object and the codec
+        const SkImageInfo& imageInfo = SkImageInfo::Make(decoderMgr->dinfo()->image_width,
+                decoderMgr->dinfo()->image_height, colorType, kOpaque_SkAlphaType);
+        *codecOut = SkNEW_ARGS(SkJpegCodec, (imageInfo, stream, decoderMgr.detach()));
+    } else {
+        SkASSERT(NULL != decoderMgrOut);
+        *decoderMgrOut = decoderMgr.detach();
+    }
+    return true;
+}
+
+SkCodec* SkJpegCodec::NewFromStream(SkStream* stream) {
+    SkAutoTDelete<SkStream> streamDeleter(stream);
+    SkCodec* codec = NULL;
+    if (ReadHeader(stream,  &codec, NULL)) {
+        // Codec has taken ownership of the stream, we do not need to delete it
+        SkASSERT(codec);
+        streamDeleter.detach();
+        return codec;
+    }
+    return NULL;
+}
+
+SkJpegCodec::SkJpegCodec(const SkImageInfo& srcInfo, SkStream* stream,
+        JpegDecoderMgr* decoderMgr)
+    : INHERITED(srcInfo, stream)
+    , fDecoderMgr(decoderMgr)
+{}
+
+/*
+ * Return a valid set of output dimensions for this decoder, given an input scale
+ */
+SkISize SkJpegCodec::onGetScaledDimensions(float desiredScale) const {
+    // libjpeg supports scaling by 1/1, 1/2, 1/4, and 1/8, so we will support these as well
+    long scale;
+    if (desiredScale > 0.75f) {
+        scale = 1;
+    } else if (desiredScale > 0.375f) {
+        scale = 2;
+    } else if (desiredScale > 0.1875f) {
+        scale = 4;
+    } else {
+        scale = 8;
+    }
+
+    // Set up a fake decompress struct in order to use libjpeg to calculate output dimensions
+    jpeg_decompress_struct dinfo;
+    dinfo.image_width = this->getInfo().width();
+    dinfo.image_height = this->getInfo().height();
+    dinfo.global_state = DSTATE_READY;
+    dinfo.num_components = 0;
+    dinfo.scale_num = 1;
+    dinfo.scale_denom = scale;
+    jpeg_calc_output_dimensions(&dinfo);
+
+    // Return the calculated output dimensions for the given scale
+    return SkISize::Make(dinfo.output_width, dinfo.output_height);
+}
+
+/*
+ * Checks if the conversion between the input image and the requested output
+ * image has been implemented
+ */
+static bool conversion_possible(const SkImageInfo& dst,
+                                const SkImageInfo& src) {
+    // Ensure that the profile type is unchanged
+    if (dst.profileType() != src.profileType()) {
+        return false;
+    }
+
+    // Ensure that the alpha type is opaque
+    if (kOpaque_SkAlphaType != dst.alphaType()) {
+        return false;
+    }
+
+    // Always allow kN32 as the color type
+    if (kN32_SkColorType == dst.colorType()) {
+        return true;
+    }
+
+    // Otherwise require that the destination color type match our recommendation
+    return dst.colorType() == src.colorType();
+}
+
+/*
+ * Performs the jpeg decode
+ */
+SkCodec::Result SkJpegCodec::onGetPixels(const SkImageInfo& dstInfo,
+                                         void* dst, size_t dstRowBytes,
+                                         const Options& options, SkPMColor*, int*) {
+    // Rewind the stream if needed
+    SkCodec::RewindState rewindState = this->rewindIfNeeded();
+    if (rewindState == kCouldNotRewind_RewindState) {
+        return kCouldNotRewind;
+    } else if (rewindState == kRewound_RewindState) {
+        JpegDecoderMgr* decoderMgr = NULL;
+        if (!ReadHeader(this->stream(), NULL, &decoderMgr)) {
+            return kCouldNotRewind;
+        }
+        SkASSERT(NULL != decoderMgr);
+        fDecoderMgr.reset(decoderMgr);
+    }
+
+    // Set the jump location for libjpeg errors
+    if (setjmp(fDecoderMgr->errorMgr()->fJmpBuf)) {
+        return fDecoderMgr->returnFailure("setjmp", kInvalidInput);
+    }
+
+    // Check if we can decode to the requested destination
+    if (!conversion_possible(dstInfo, this->getInfo())) {
+        return fDecoderMgr->returnFailure("conversion_possible", kInvalidConversion);
+    }
+    // Check if we can scale to the requested dimensions
+    // libjpeg can scale to 1/1, 1/2, 1/4, and 1/8
+    SkASSERT(1 == fDecoderMgr->dinfo()->scale_num);
+    SkASSERT(1 == fDecoderMgr->dinfo()->scale_denom);
+    jpeg_calc_output_dimensions(fDecoderMgr->dinfo());
+    const uint32_t dstWidth = dstInfo.width();
+    const uint32_t dstHeight = dstInfo.height();
+    while (fDecoderMgr->dinfo()->output_width != dstWidth ||
+            fDecoderMgr->dinfo()->output_height != dstHeight) {
+
+        // Return a failure if we have tried all of the possible scales
+        if (8 == fDecoderMgr->dinfo()->scale_denom ||
+                dstWidth > fDecoderMgr->dinfo()->output_width ||
+                dstHeight > fDecoderMgr->dinfo()->output_height) {
+            return fDecoderMgr->returnFailure("cannot scale to requested dims", kInvalidScale);
+        }
+
+        // Try the next scale
+        fDecoderMgr->dinfo()->scale_denom *= 2;
+        jpeg_calc_output_dimensions(fDecoderMgr->dinfo());
+    }
+
+    // Now, given valid output dimensions, we can start the decompress
+    if (!jpeg_start_decompress(fDecoderMgr->dinfo())) {
+        return fDecoderMgr->returnFailure("startDecompress", kInvalidInput);
+    }
+
+    // Create the swizzler
+    SkSwizzler::SrcConfig srcConfig = get_src_config(fDecoderMgr->dinfo());
+    SkAutoTDelete<SkSwizzler> swizzler(SkSwizzler::CreateSwizzler(srcConfig, NULL, dstInfo, dst, dstRowBytes, options.fZeroInitialized));
+    if (NULL == swizzler) {
+        return fDecoderMgr->returnFailure("getSwizzler", kInvalidInput);
+    }
+    const uint32_t srcBytesPerPixel = SkSwizzler::BytesPerPixel(srcConfig);
+
+    // This is usually 1, but can also be 2 or 4.
+    // If we wanted to always read one row at a time, we could, but we will save space and time
+    // by using the recommendation from libjpeg.
+    const uint32_t rowsPerDecode = fDecoderMgr->dinfo()->rec_outbuf_height;
+    SkASSERT(rowsPerDecode <= 4);
+
+    // Create a buffer to contain decoded rows (libjpeg requires a 2D array)
+    const uint32_t srcRowBytes = srcBytesPerPixel * dstWidth;
+    SkAutoTDeleteArray<uint8_t> srcBuffer(SkNEW_ARRAY(uint8_t, srcRowBytes * rowsPerDecode));
+    JSAMPLE* srcRows[4];
+    uint8_t* srcPtr = srcBuffer.get();
+    for (uint8_t i = 0; i < rowsPerDecode; i++) {
+        srcRows[i] = (JSAMPLE*) srcPtr;
+        srcPtr += srcRowBytes;
+    }
+
+    // Ensure that we loop enough times to decode all of the rows
+    // libjpeg will prevent us from reading past the bottom of the image
+    for (uint32_t y = 0; y < dstHeight + rowsPerDecode - 1; y += rowsPerDecode) {
+        // Read rows of the image
+        uint32_t rowsDecoded = jpeg_read_scanlines(fDecoderMgr->dinfo(), srcRows, rowsPerDecode);
+
+        // Convert to RGB if necessary
+        if (JCS_CMYK == fDecoderMgr->dinfo()->out_color_space) {
+            convert_CMYK_to_RGB(srcRows[0], dstWidth * rowsDecoded);
+        }
+
+        // Swizzle to output destination
+        for (uint32_t i = 0; i < rowsDecoded; i++) {
+            swizzler->next(srcRows[i]);
+        }
+
+        // If we cannot read enough rows, assume the input is incomplete
+        if (rowsDecoded < rowsPerDecode && y + rowsDecoded < dstHeight) {
+            // Fill the remainder of the image with black. This error handling
+            // behavior is unspecified but SkCodec consistently uses black as
+            // the fill color for opaque images.
+            SkSwizzler::Fill(swizzler->getDstRow(), dstInfo, dstRowBytes,
+                    dstHeight - y - rowsDecoded, SK_ColorBLACK, NULL);

[scroggo, 2015/04/15 00:31:06]

Maybe add a comment that SK_ColorBLACK is valid to use for kGray as well.

[msarett, 2015/04/15 12:43:11]

Done.

+
+            // Prevent libjpeg from failing
+            fDecoderMgr->dinfo()->output_scanline = dstHeight;
+
+            // Finish the decode and indicate that the input was incomplete.
+            jpeg_finish_decompress(fDecoderMgr->dinfo());
+            return fDecoderMgr->returnFailure("Incomplete image data", kIncompleteInput);
+        }
+    }
+    jpeg_finish_decompress(fDecoderMgr->dinfo());
+
+    return kSuccess;
+}