root/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp

DEFINITIONS

1. rgbOutputColorSpace
2. rgbOutputColorSpace
3. turboSwizzled
4. colorSpaceHasAlpha
5. rgbOutputColorSpace
6. colorSpaceHasAlpha
7. dctMethod
8. ditherMode
9. dctMethod
10. ditherMode
11. doFancyUpsampling
12. doFancyUpsampling
13. readUint16
14. readUint32
15. checkExifHeader
16. readImageOrientation
17. readColorProfile
18. m_transform
19. close
20. skipBytes
21. decode
22. info
23. samples
24. decoder
25. colorTransform
26. createColorTransform
27. error_exit
28. init_source
29. skip_input_data
30. fill_input_buffer
31. term_source
32. isSizeAvailable
33. setSize
34. setDecodedSize
35. desiredScaleNumerator
36. frameBufferAtIndex
37. setFailed
38. setPixel
39. outputRows
40. outputScanlines
41. jpegComplete
42. decode

/*
 * Copyright (C) 2006 Apple Computer, Inc.
 *
 * Portions are Copyright (C) 2001-6 mozilla.org
 *
 * Other contributors:
 *   Stuart Parmenter <stuart@mozilla.com>
 *
 * Copyright (C) 2007-2009 Torch Mobile, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 *
 * Alternatively, the contents of this file may be used under the terms
 * of either the Mozilla Public License Version 1.1, found at
 * http://www.mozilla.org/MPL/ (the "MPL") or the GNU General Public
 * License Version 2.0, found at http://www.fsf.org/copyleft/gpl.html
 * (the "GPL"), in which case the provisions of the MPL or the GPL are
 * applicable instead of those above.  If you wish to allow use of your
 * version of this file only under the terms of one of those two
 * licenses (the MPL or the GPL) and not to allow others to use your
 * version of this file under the LGPL, indicate your decision by
 * deletingthe provisions above and replace them with the notice and
 * other provisions required by the MPL or the GPL, as the case may be.
 * If you do not delete the provisions above, a recipient may use your
 * version of this file under any of the LGPL, the MPL or the GPL.
 */

#include "config.h"
#include "platform/image-decoders/jpeg/JPEGImageDecoder.h"

#include "platform/PlatformInstrumentation.h"
#include "wtf/PassOwnPtr.h"
#include "wtf/dtoa/utils.h"

extern "C" {
#include <stdio.h> // jpeglib.h needs stdio FILE.
#include "jpeglib.h"
#if USE(ICCJPEG)
#include "iccjpeg.h"
#endif
#if USE(QCMSLIB)
#include "qcms.h"
#endif
#include <setjmp.h>
}

#if CPU(BIG_ENDIAN) || CPU(MIDDLE_ENDIAN)
#error Blink assumes a little-endian target.
#endif

#if defined(JCS_ALPHA_EXTENSIONS)
#define TURBO_JPEG_RGB_SWIZZLE
#if SK_B32_SHIFT // Output little-endian RGBA pixels (Android).
inline J_COLOR_SPACE rgbOutputColorSpace() { return JCS_EXT_RGBA; }
#else // Output little-endian BGRA pixels.
inline J_COLOR_SPACE rgbOutputColorSpace() { return JCS_EXT_BGRA; }
#endif
inline bool turboSwizzled(J_COLOR_SPACE colorSpace) { return colorSpace == JCS_EXT_RGBA || colorSpace == JCS_EXT_BGRA; }
inline bool colorSpaceHasAlpha(J_COLOR_SPACE colorSpace) { return turboSwizzled(colorSpace); }
#else
inline J_COLOR_SPACE rgbOutputColorSpace() { return JCS_RGB; }
inline bool colorSpaceHasAlpha(J_COLOR_SPACE) { return false; }
#endif

#if USE(LOW_QUALITY_IMAGE_NO_JPEG_DITHERING)
inline J_DCT_METHOD dctMethod() { return JDCT_IFAST; }
inline J_DITHER_MODE ditherMode() { return JDITHER_NONE; }
#else
inline J_DCT_METHOD dctMethod() { return JDCT_ISLOW; }
inline J_DITHER_MODE ditherMode() { return JDITHER_FS; }
#endif

#if USE(LOW_QUALITY_IMAGE_NO_JPEG_FANCY_UPSAMPLING)
inline bool doFancyUpsampling() { return false; }
#else
inline bool doFancyUpsampling() { return true; }
#endif

namespace {

const int exifMarker = JPEG_APP0 + 1;

// JPEG only supports a denominator of 8.
const unsigned scaleDenominator = 8;

} // namespace

namespace WebCore {

struct decoder_error_mgr {
    struct jpeg_error_mgr pub; // "public" fields for IJG library
    jmp_buf setjmp_buffer;     // For handling catastropic errors
};

enum jstate {
    JPEG_HEADER,                 // Reading JFIF headers
    JPEG_START_DECOMPRESS,
    JPEG_DECOMPRESS_PROGRESSIVE, // Output progressive pixels
    JPEG_DECOMPRESS_SEQUENTIAL,  // Output sequential pixels
    JPEG_DONE,
    JPEG_ERROR
};

void init_source(j_decompress_ptr jd);
boolean fill_input_buffer(j_decompress_ptr jd);
void skip_input_data(j_decompress_ptr jd, long num_bytes);
void term_source(j_decompress_ptr jd);
void error_exit(j_common_ptr cinfo);

// Implementation of a JPEG src object that understands our state machine
struct decoder_source_mgr {
    // public fields; must be first in this struct!
    struct jpeg_source_mgr pub;

    JPEGImageReader* decoder;
};

static unsigned readUint16(JOCTET* data, bool isBigEndian)
{
    if (isBigEndian)
        return (GETJOCTET(data[0]) << 8) | GETJOCTET(data[1]);
    return (GETJOCTET(data[1]) << 8) | GETJOCTET(data[0]);
}

static unsigned readUint32(JOCTET* data, bool isBigEndian)
{
    if (isBigEndian)
        return (GETJOCTET(data[0]) << 24) | (GETJOCTET(data[1]) << 16) | (GETJOCTET(data[2]) << 8) | GETJOCTET(data[3]);
    return (GETJOCTET(data[3]) << 24) | (GETJOCTET(data[2]) << 16) | (GETJOCTET(data[1]) << 8) | GETJOCTET(data[0]);
}

static bool checkExifHeader(jpeg_saved_marker_ptr marker, bool& isBigEndian, unsigned& ifdOffset)
{
    // For exif data, the APP1 block is followed by 'E', 'x', 'i', 'f', '\0',
    // then a fill byte, and then a tiff file that contains the metadata.
    // A tiff file starts with 'I', 'I' (intel / little endian byte order) or
    // 'M', 'M' (motorola / big endian byte order), followed by (uint16_t)42,
    // followed by an uint32_t with the offset to the tag block, relative to the
    // tiff file start.
    const unsigned exifHeaderSize = 14;
    if (!(marker->marker == exifMarker
        && marker->data_length >= exifHeaderSize
        && marker->data[0] == 'E'
        && marker->data[1] == 'x'
        && marker->data[2] == 'i'
        && marker->data[3] == 'f'
        && marker->data[4] == '\0'
        // data[5] is a fill byte
        && ((marker->data[6] == 'I' && marker->data[7] == 'I')
            || (marker->data[6] == 'M' && marker->data[7] == 'M'))))
        return false;

    isBigEndian = marker->data[6] == 'M';
    if (readUint16(marker->data + 8, isBigEndian) != 42)
        return false;

    ifdOffset = readUint32(marker->data + 10, isBigEndian);
    return true;
}

static ImageOrientation readImageOrientation(jpeg_decompress_struct* info)
{
    // The JPEG decoder looks at EXIF metadata.
    // FIXME: Possibly implement XMP and IPTC support.
    const unsigned orientationTag = 0x112;
    const unsigned shortType = 3;
    for (jpeg_saved_marker_ptr marker = info->marker_list; marker; marker = marker->next) {
        bool isBigEndian;
        unsigned ifdOffset;
        if (!checkExifHeader(marker, isBigEndian, ifdOffset))
            continue;
        const unsigned offsetToTiffData = 6; // Account for 'Exif\0<fill byte>' header.
        if (marker->data_length < offsetToTiffData || ifdOffset >= marker->data_length - offsetToTiffData)
            continue;
        ifdOffset += offsetToTiffData;

        // The jpeg exif container format contains a tiff block for metadata.
        // A tiff image file directory (ifd) consists of a uint16_t describing
        // the number of ifd entries, followed by that many entries.
        // When touching this code, it's useful to look at the tiff spec:
        // http://partners.adobe.com/public/developer/en/tiff/TIFF6.pdf
        JOCTET* ifd = marker->data + ifdOffset;
        JOCTET* end = marker->data + marker->data_length;
        if (end - ifd < 2)
            continue;
        unsigned tagCount = readUint16(ifd, isBigEndian);
        ifd += 2; // Skip over the uint16 that was just read.

        // Every ifd entry is 2 bytes of tag, 2 bytes of contents datatype,
        // 4 bytes of number-of-elements, and 4 bytes of either offset to the
        // tag data, or if the data is small enough, the inlined data itself.
        const int ifdEntrySize = 12;
        for (unsigned i = 0; i < tagCount && end - ifd >= ifdEntrySize; ++i, ifd += ifdEntrySize) {
            unsigned tag = readUint16(ifd, isBigEndian);
            unsigned type = readUint16(ifd + 2, isBigEndian);
            unsigned count = readUint32(ifd + 4, isBigEndian);
            if (tag == orientationTag && type == shortType && count == 1)
                return ImageOrientation::fromEXIFValue(readUint16(ifd + 8, isBigEndian));
        }
    }

    return ImageOrientation();
}

#if USE(QCMSLIB)
static void readColorProfile(jpeg_decompress_struct* info, ColorProfile& colorProfile)
{
#if USE(ICCJPEG)
    JOCTET* profile;
    unsigned profileLength;

    if (!read_icc_profile(info, &profile, &profileLength))
        return;

    // Only accept RGB color profiles from input class devices.
    bool ignoreProfile = false;
    char* profileData = reinterpret_cast<char*>(profile);
    if (profileLength < ImageDecoder::iccColorProfileHeaderLength)
        ignoreProfile = true;
    else if (!ImageDecoder::rgbColorProfile(profileData, profileLength))
        ignoreProfile = true;
    else if (!ImageDecoder::inputDeviceColorProfile(profileData, profileLength))
        ignoreProfile = true;

    ASSERT(colorProfile.isEmpty());
    if (!ignoreProfile)
        colorProfile.append(profileData, profileLength);
    free(profile);
#endif
}
#endif

class JPEGImageReader {
    WTF_MAKE_FAST_ALLOCATED;
public:
    JPEGImageReader(JPEGImageDecoder* decoder)
        : m_decoder(decoder)
        , m_bufferLength(0)
        , m_bytesToSkip(0)
        , m_state(JPEG_HEADER)
        , m_samples(0)
#if USE(QCMSLIB)
        , m_transform(0)
#endif
    {
        memset(&m_info, 0, sizeof(jpeg_decompress_struct));

        // We set up the normal JPEG error routines, then override error_exit.
        m_info.err = jpeg_std_error(&m_err.pub);
        m_err.pub.error_exit = error_exit;

        // Allocate and initialize JPEG decompression object.
        jpeg_create_decompress(&m_info);

        decoder_source_mgr* src = 0;
        if (!m_info.src) {
            src = (decoder_source_mgr*)fastZeroedMalloc(sizeof(decoder_source_mgr));
            if (!src) {
                m_state = JPEG_ERROR;
                return;
            }
        }

        m_info.src = (jpeg_source_mgr*)src;

        // Set up callback functions.
        src->pub.init_source = init_source;
        src->pub.fill_input_buffer = fill_input_buffer;
        src->pub.skip_input_data = skip_input_data;
        src->pub.resync_to_restart = jpeg_resync_to_restart;
        src->pub.term_source = term_source;
        src->decoder = this;

#if USE(ICCJPEG)
        // Retain ICC color profile markers for color management.
        setup_read_icc_profile(&m_info);
#endif

        // Keep APP1 blocks, for obtaining exif data.
        jpeg_save_markers(&m_info, exifMarker, 0xFFFF);
    }

    ~JPEGImageReader()
    {
        close();
    }

    void close()
    {
        decoder_source_mgr* src = (decoder_source_mgr*)m_info.src;
        if (src)
            fastFree(src);
        m_info.src = 0;

#if USE(QCMSLIB)
        if (m_transform)
            qcms_transform_release(m_transform);
        m_transform = 0;
#endif
        jpeg_destroy_decompress(&m_info);
    }

    void skipBytes(long numBytes)
    {
        decoder_source_mgr* src = (decoder_source_mgr*)m_info.src;
        long bytesToSkip = std::min(numBytes, (long)src->pub.bytes_in_buffer);
        src->pub.bytes_in_buffer -= (size_t)bytesToSkip;
        src->pub.next_input_byte += bytesToSkip;

        m_bytesToSkip = std::max(numBytes - bytesToSkip, static_cast<long>(0));
    }

    bool decode(const SharedBuffer& data, bool onlySize)
    {
        unsigned newByteCount = data.size() - m_bufferLength;
        unsigned readOffset = m_bufferLength - m_info.src->bytes_in_buffer;

        m_info.src->bytes_in_buffer += newByteCount;
        m_info.src->next_input_byte = (JOCTET*)(data.data()) + readOffset;

        // If we still have bytes to skip, try to skip those now.
        if (m_bytesToSkip)
            skipBytes(m_bytesToSkip);

        m_bufferLength = data.size();

        // We need to do the setjmp here. Otherwise bad things will happen
        if (setjmp(m_err.setjmp_buffer))
            return m_decoder->setFailed();

        switch (m_state) {
        case JPEG_HEADER:
            // Read file parameters with jpeg_read_header().
            if (jpeg_read_header(&m_info, true) == JPEG_SUSPENDED)
                return false; // I/O suspension.

            switch (m_info.jpeg_color_space) {
            case JCS_GRAYSCALE:
            case JCS_RGB:
            case JCS_YCbCr:
                // libjpeg can convert GRAYSCALE and YCbCr image pixels to RGB.
                m_info.out_color_space = rgbOutputColorSpace();
#if defined(TURBO_JPEG_RGB_SWIZZLE)
                if (m_info.saw_JFIF_marker)
                    break;
                // FIXME: Swizzle decoding does not support Adobe transform=0
                // images (yet), so revert to using JSC_RGB in that case.
                if (m_info.saw_Adobe_marker && !m_info.Adobe_transform)
                    m_info.out_color_space = JCS_RGB;
#endif
                break;
            case JCS_CMYK:
            case JCS_YCCK:
                // libjpeg can convert YCCK to CMYK, but neither to RGB, so we
                // manually convert CMKY to RGB.
                m_info.out_color_space = JCS_CMYK;
                break;
            default:
                return m_decoder->setFailed();
            }

            m_state = JPEG_START_DECOMPRESS;

            // We can fill in the size now that the header is available.
            if (!m_decoder->setSize(m_info.image_width, m_info.image_height))
                return false;

            // Calculate and set decoded size.
            m_info.scale_num = m_decoder->desiredScaleNumerator();
            m_info.scale_denom = scaleDenominator;
            jpeg_calc_output_dimensions(&m_info);
            m_decoder->setDecodedSize(m_info.output_width, m_info.output_height);

            m_decoder->setOrientation(readImageOrientation(info()));

#if USE(QCMSLIB)
            // Allow color management of the decoded RGBA pixels if possible.
            if (!m_decoder->ignoresGammaAndColorProfile()) {
                ColorProfile colorProfile;
                readColorProfile(info(), colorProfile);
                createColorTransform(colorProfile, colorSpaceHasAlpha(m_info.out_color_space));
#if defined(TURBO_JPEG_RGB_SWIZZLE)
                // Input RGBA data to qcms. Note: restored to BGRA on output.
                if (m_transform && m_info.out_color_space == JCS_EXT_BGRA)
                    m_info.out_color_space = JCS_EXT_RGBA;
#endif
            }
#endif
            // Don't allocate a giant and superfluous memory buffer when the
            // image is a sequential JPEG.
            m_info.buffered_image = jpeg_has_multiple_scans(&m_info);

            if (onlySize) {
                // We can stop here. Reduce our buffer length and available data.
                m_bufferLength -= m_info.src->bytes_in_buffer;
                m_info.src->bytes_in_buffer = 0;
                return true;
            }
        // FALL THROUGH

        case JPEG_START_DECOMPRESS:
            // Set parameters for decompression.
            // FIXME -- Should reset dct_method and dither mode for final pass
            // of progressive JPEG.
            m_info.dct_method = dctMethod();
            m_info.dither_mode = ditherMode();
            m_info.do_fancy_upsampling = doFancyUpsampling();
            m_info.enable_2pass_quant = false;
            m_info.do_block_smoothing = true;

            // Make a one-row-high sample array that will go away when done with
            // image. Always make it big enough to hold an RGB row. Since this
            // uses the IJG memory manager, it must be allocated before the call
            // to jpeg_start_compress().
            // FIXME: note that some output color spaces do not need the samples
            // buffer. Remove this allocation for those color spaces.
            m_samples = (*m_info.mem->alloc_sarray)(reinterpret_cast<j_common_ptr>(&m_info), JPOOL_IMAGE, m_info.output_width * 4, 1);

            // Start decompressor.
            if (!jpeg_start_decompress(&m_info))
                return false; // I/O suspension.

            // If this is a progressive JPEG ...
            m_state = (m_info.buffered_image) ? JPEG_DECOMPRESS_PROGRESSIVE : JPEG_DECOMPRESS_SEQUENTIAL;
        // FALL THROUGH

        case JPEG_DECOMPRESS_SEQUENTIAL:
            if (m_state == JPEG_DECOMPRESS_SEQUENTIAL) {

                if (!m_decoder->outputScanlines())
                    return false; // I/O suspension.

                // If we've completed image output...
                ASSERT(m_info.output_scanline == m_info.output_height);
                m_state = JPEG_DONE;
            }
        // FALL THROUGH

        case JPEG_DECOMPRESS_PROGRESSIVE:
            if (m_state == JPEG_DECOMPRESS_PROGRESSIVE) {
                int status;
                do {
                    status = jpeg_consume_input(&m_info);
                } while ((status != JPEG_SUSPENDED) && (status != JPEG_REACHED_EOI));

                for (;;) {
                    if (!m_info.output_scanline) {
                        int scan = m_info.input_scan_number;

                        // If we haven't displayed anything yet
                        // (output_scan_number == 0) and we have enough data for
                        // a complete scan, force output of the last full scan.
                        if (!m_info.output_scan_number && (scan > 1) && (status != JPEG_REACHED_EOI))
                            --scan;

                        if (!jpeg_start_output(&m_info, scan))
                            return false; // I/O suspension.
                    }

                    if (m_info.output_scanline == 0xffffff)
                        m_info.output_scanline = 0;

                    // If outputScanlines() fails, it deletes |this|. Therefore,
                    // copy the decoder pointer and use it to check for failure
                    // to avoid member access in the failure case.
                    JPEGImageDecoder* decoder = m_decoder;
                    if (!decoder->outputScanlines()) {
                        if (decoder->failed()) // Careful; |this| is deleted.
                            return false;
                        if (!m_info.output_scanline)
                            // Didn't manage to read any lines - flag so we
                            // don't call jpeg_start_output() multiple times for
                            // the same scan.
                            m_info.output_scanline = 0xffffff;
                        return false; // I/O suspension.
                    }

                    if (m_info.output_scanline == m_info.output_height) {
                        if (!jpeg_finish_output(&m_info))
                            return false; // I/O suspension.

                        if (jpeg_input_complete(&m_info) && (m_info.input_scan_number == m_info.output_scan_number))
                            break;

                        m_info.output_scanline = 0;
                    }
                }

                m_state = JPEG_DONE;
            }
        // FALL THROUGH

        case JPEG_DONE:
            // Finish decompression.
            return jpeg_finish_decompress(&m_info);

        case JPEG_ERROR:
            // We can get here if the constructor failed.
            return m_decoder->setFailed();
        }

        return true;
    }

    jpeg_decompress_struct* info() { return &m_info; }
    JSAMPARRAY samples() const { return m_samples; }
    JPEGImageDecoder* decoder() { return m_decoder; }
#if USE(QCMSLIB)
    qcms_transform* colorTransform() const { return m_transform; }

    void createColorTransform(const ColorProfile& colorProfile, bool hasAlpha)
    {
        if (m_transform)
            qcms_transform_release(m_transform);
        m_transform = 0;

        if (colorProfile.isEmpty())
            return;
        qcms_profile* deviceProfile = ImageDecoder::qcmsOutputDeviceProfile();
        if (!deviceProfile)
            return;
        qcms_profile* inputProfile = qcms_profile_from_memory(colorProfile.data(), colorProfile.size());
        if (!inputProfile)
            return;
        // We currently only support color profiles for RGB profiled images.
        ASSERT(icSigRgbData == qcms_profile_get_color_space(inputProfile));
        qcms_data_type dataFormat = hasAlpha ? QCMS_DATA_RGBA_8 : QCMS_DATA_RGB_8;
        // FIXME: Don't force perceptual intent if the image profile contains an intent.
        m_transform = qcms_transform_create(inputProfile, dataFormat, deviceProfile, dataFormat, QCMS_INTENT_PERCEPTUAL);
        qcms_profile_release(inputProfile);
    }
#endif

private:
    JPEGImageDecoder* m_decoder;
    unsigned m_bufferLength;
    int m_bytesToSkip;

    jpeg_decompress_struct m_info;
    decoder_error_mgr m_err;
    jstate m_state;

    JSAMPARRAY m_samples;

#if USE(QCMSLIB)
    qcms_transform* m_transform;
#endif
};

// Override the standard error method in the IJG JPEG decoder code.
void error_exit(j_common_ptr cinfo)
{
    // Return control to the setjmp point.
    decoder_error_mgr *err = reinterpret_cast_ptr<decoder_error_mgr *>(cinfo->err);
    longjmp(err->setjmp_buffer, -1);
}

void init_source(j_decompress_ptr)
{
}

void skip_input_data(j_decompress_ptr jd, long num_bytes)
{
    decoder_source_mgr *src = (decoder_source_mgr *)jd->src;
    src->decoder->skipBytes(num_bytes);
}

boolean fill_input_buffer(j_decompress_ptr)
{
    // Our decode step always sets things up properly, so if this method is ever
    // called, then we have hit the end of the buffer.  A return value of false
    // indicates that we have no data to supply yet.
    return false;
}

void term_source(j_decompress_ptr jd)
{
    decoder_source_mgr *src = (decoder_source_mgr *)jd->src;
    src->decoder->decoder()->jpegComplete();
}

JPEGImageDecoder::JPEGImageDecoder(ImageSource::AlphaOption alphaOption,
    ImageSource::GammaAndColorProfileOption gammaAndColorProfileOption,
    size_t maxDecodedBytes)
    : ImageDecoder(alphaOption, gammaAndColorProfileOption, maxDecodedBytes)
{
}

JPEGImageDecoder::~JPEGImageDecoder()
{
}

bool JPEGImageDecoder::isSizeAvailable()
{
    if (!ImageDecoder::isSizeAvailable())
         decode(true);

    return ImageDecoder::isSizeAvailable();
}

bool JPEGImageDecoder::setSize(unsigned width, unsigned height)
{
    if (!ImageDecoder::setSize(width, height))
        return false;

    if (!desiredScaleNumerator())
        return setFailed();

    setDecodedSize(width, height);
    return true;
}

void JPEGImageDecoder::setDecodedSize(unsigned width, unsigned height)
{
    m_decodedSize = IntSize(width, height);
}

unsigned JPEGImageDecoder::desiredScaleNumerator() const
{
    size_t originalBytes = size().width() * size().height() * 4;
    if (originalBytes <= m_maxDecodedBytes) {
        return scaleDenominator;
    }

    // Downsample according to the maximum decoded size.
    unsigned scaleNumerator = static_cast<unsigned>(floor(sqrt(
        // MSVC needs explicit parameter type for sqrt().
        static_cast<float>(m_maxDecodedBytes * scaleDenominator * scaleDenominator / originalBytes))));

    return scaleNumerator;
}

ImageFrame* JPEGImageDecoder::frameBufferAtIndex(size_t index)
{
    if (index)
        return 0;

    if (m_frameBufferCache.isEmpty()) {
        m_frameBufferCache.resize(1);
        m_frameBufferCache[0].setPremultiplyAlpha(m_premultiplyAlpha);
    }

    ImageFrame& frame = m_frameBufferCache[0];
    if (frame.status() != ImageFrame::FrameComplete) {
        PlatformInstrumentation::willDecodeImage("JPEG");
        decode(false);
        PlatformInstrumentation::didDecodeImage();
    }

    frame.notifyBitmapIfPixelsChanged();
    return &frame;
}

bool JPEGImageDecoder::setFailed()
{
    m_reader.clear();
    return ImageDecoder::setFailed();
}

template <J_COLOR_SPACE colorSpace> void setPixel(ImageFrame& buffer, ImageFrame::PixelData* pixel, JSAMPARRAY samples, int column)
{
    JSAMPLE* jsample = *samples + column * (colorSpace == JCS_RGB ? 3 : 4);

    switch (colorSpace) {
    case JCS_RGB:
        buffer.setRGBARaw(pixel, jsample[0], jsample[1], jsample[2], 255);
        break;
    case JCS_CMYK:
        // Source is 'Inverted CMYK', output is RGB.
        // See: http://www.easyrgb.com/math.php?MATH=M12#text12
        // Or: http://www.ilkeratalay.com/colorspacesfaq.php#rgb
        // From CMYK to CMY:
        // X =   X    * (1 -   K   ) +   K  [for X = C, M, or Y]
        // Thus, from Inverted CMYK to CMY is:
        // X = (1-iX) * (1 - (1-iK)) + (1-iK) => 1 - iX*iK
        // From CMY (0..1) to RGB (0..1):
        // R = 1 - C => 1 - (1 - iC*iK) => iC*iK  [G and B similar]
        unsigned k = jsample[3];
        buffer.setRGBARaw(pixel, jsample[0] * k / 255, jsample[1] * k / 255, jsample[2] * k / 255, 255);
        break;
    }
}

template <J_COLOR_SPACE colorSpace> bool outputRows(JPEGImageReader* reader, ImageFrame& buffer)
{
    JSAMPARRAY samples = reader->samples();
    jpeg_decompress_struct* info = reader->info();
    int width = info->output_width;

    while (info->output_scanline < info->output_height) {
        // jpeg_read_scanlines will increase the scanline counter, so we
        // save the scanline before calling it.
        int y = info->output_scanline;
        // Request one scanline: returns 0 or 1 scanlines.
        if (jpeg_read_scanlines(info, samples, 1) != 1)
            return false;
#if USE(QCMSLIB)
        if (reader->colorTransform() && colorSpace == JCS_RGB)
            qcms_transform_data(reader->colorTransform(), *samples, *samples, width);
#endif
        ImageFrame::PixelData* pixel = buffer.getAddr(0, y);
        for (int x = 0; x < width; ++pixel, ++x)
            setPixel<colorSpace>(buffer, pixel, samples, x);
    }

    buffer.setPixelsChanged(true);
    return true;
}

bool JPEGImageDecoder::outputScanlines()
{
    if (m_frameBufferCache.isEmpty())
        return false;

    jpeg_decompress_struct* info = m_reader->info();

    // Initialize the framebuffer if needed.
    ImageFrame& buffer = m_frameBufferCache[0];
    if (buffer.status() == ImageFrame::FrameEmpty) {
        ASSERT(info->output_width == static_cast<JDIMENSION>(m_decodedSize.width()));
        ASSERT(info->output_height == static_cast<JDIMENSION>(m_decodedSize.height()));

        if (!buffer.setSize(info->output_width, info->output_height))
            return setFailed();
        buffer.setStatus(ImageFrame::FramePartial);
        // The buffer is transparent outside the decoded area while the image is
        // loading. The completed image will be marked fully opaque in jpegComplete().
        buffer.setHasAlpha(true);

        // For JPEGs, the frame always fills the entire image.
        buffer.setOriginalFrameRect(IntRect(IntPoint(), size()));
    }

#if defined(TURBO_JPEG_RGB_SWIZZLE)
    if (turboSwizzled(info->out_color_space)) {
        while (info->output_scanline < info->output_height) {
            unsigned char* row = reinterpret_cast<unsigned char*>(buffer.getAddr(0, info->output_scanline));
            if (jpeg_read_scanlines(info, &row, 1) != 1)
                return false;
#if USE(QCMSLIB)
            if (qcms_transform* transform = m_reader->colorTransform())
                qcms_transform_data_type(transform, row, row, info->output_width, rgbOutputColorSpace() == JCS_EXT_BGRA ? QCMS_OUTPUT_BGRX : QCMS_OUTPUT_RGBX);
#endif
        }
        buffer.setPixelsChanged(true);
        return true;
    }
#endif

    switch (info->out_color_space) {
    case JCS_RGB:
        return outputRows<JCS_RGB>(m_reader.get(), buffer);
    case JCS_CMYK:
        return outputRows<JCS_CMYK>(m_reader.get(), buffer);
    default:
        ASSERT_NOT_REACHED();
    }

    return setFailed();
}

void JPEGImageDecoder::jpegComplete()
{
    if (m_frameBufferCache.isEmpty())
        return;

    // Hand back an appropriately sized buffer, even if the image ended up being
    // empty.
    ImageFrame& buffer = m_frameBufferCache[0];
    buffer.setHasAlpha(false);
    buffer.setStatus(ImageFrame::FrameComplete);
}

void JPEGImageDecoder::decode(bool onlySize)
{
    if (failed())
        return;

    if (!m_reader) {
        m_reader = adoptPtr(new JPEGImageReader(this));
    }

    // If we couldn't decode the image but we've received all the data, decoding
    // has failed.
    if (!m_reader->decode(*m_data, onlySize) && isAllDataReceived())
        setFailed();
    // If we're done decoding the image, we don't need the JPEGImageReader
    // anymore.  (If we failed, |m_reader| has already been cleared.)
    else if (!m_frameBufferCache.isEmpty() && (m_frameBufferCache[0].status() == ImageFrame::FrameComplete))
        m_reader.clear();
}

}