qjpeghandler.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:critical reason:data-parser
 
#include "qjpeghandler_p.h"
 
#include <qbuffer.h>
#include <qcolorspace.h>
#include <qcolortransform.h>
#include <qdebug.h>
#include <qimage.h>
#include <qimagereader.h>
#include <qlist.h>
#include <qloggingcategory.h>
#include <qmath.h>
#include <qvariant.h>
#include <private/qicc_p.h>
#include <private/qsimd_p.h>
#include <private/qimage_p.h>   // for qt_getImageText
 
#include <limits>
#include <stdio.h>      // jpeglib needs this to be pre-included
#include <setjmp.h>
 
#ifdef FAR
#undef FAR
#endif
 
// including jpeglib.h seems to be a little messy
extern "C" {
#define XMD_H           // shut JPEGlib up
#include <jpeglib.h>
#ifdef const
#  undef const          // remove crazy C hackery in jconfig.h
#endif
}
 
QT_BEGIN_NAMESPACE
 
Q_LOGGING_CATEGORY(lcJpeg, "qt.gui.imageio.jpeg")
 
QT_WARNING_DISABLE_GCC("-Wclobbered")
 
Q_GUI_EXPORT void QT_FASTCALL qt_convert_rgb888_to_rgb32(quint32 *dst, const uchar *src, int len);
typedef void (QT_FASTCALL *Rgb888ToRgb32Converter)(quint32 *dst, const uchar *src, int len);
 
struct my_error_mgr : public jpeg_error_mgr {
    jmp_buf setjmp_buffer;
};
 
extern "C" {
 
static void my_error_exit (j_common_ptr cinfo)
{
    (*cinfo->err->output_message)(cinfo);
    my_error_mgr* myerr = (my_error_mgr*) cinfo->err;
    longjmp(myerr->setjmp_buffer, 1);
}
 
static void my_output_message(j_common_ptr cinfo)
{
    char buffer[JMSG_LENGTH_MAX];
    (*cinfo->err->format_message)(cinfo, buffer);
    qCWarning(lcJpeg,"%s", buffer);
}
 
}
 
 
static const int max_buf = 4096;
 
struct my_jpeg_source_mgr : public jpeg_source_mgr {
    // Nothing dynamic - cannot rely on destruction over longjump
    QIODevice *device;
    JOCTET buffer[max_buf];
    const QBuffer *memDevice;
 
public:
    my_jpeg_source_mgr(QIODevice *device);
};
 
extern "C" {
 
static void qt_init_source(j_decompress_ptr)
{
}
 
static boolean qt_fill_input_buffer(j_decompress_ptr cinfo)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;
    qint64 num_read = 0;
    if (src->memDevice) {
        src->next_input_byte = (const JOCTET *)(src->memDevice->data().constData() + src->memDevice->pos());
        num_read = src->memDevice->data().size() - src->memDevice->pos();
        src->device->seek(src->memDevice->data().size());
    } else {
        src->next_input_byte = src->buffer;
        num_read = src->device->read((char*)src->buffer, max_buf);
    }
    if (num_read <= 0) {
        // Insert a fake EOI marker - as per jpeglib recommendation
        src->next_input_byte = src->buffer;
        src->buffer[0] = (JOCTET) 0xFF;
        src->buffer[1] = (JOCTET) JPEG_EOI;
        src->bytes_in_buffer = 2;
    } else {
        src->bytes_in_buffer = num_read;
    }
    return TRUE;
}
 
static void qt_skip_input_data(j_decompress_ptr cinfo, long num_bytes)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;
 
    // `dumb' implementation from jpeglib
 
    /* Just a dumb implementation for now.  Could use fseek() except
     * it doesn't work on pipes.  Not clear that being smart is worth
     * any trouble anyway --- large skips are infrequent.
     */
    if (num_bytes > 0) {
        while (num_bytes > (long) src->bytes_in_buffer) {  // Should not happen in case of memDevice
            num_bytes -= (long) src->bytes_in_buffer;
            (void) qt_fill_input_buffer(cinfo);
            /* note we assume that qt_fill_input_buffer will never return false,
            * so suspension need not be handled.
            */
        }
        src->next_input_byte += (size_t) num_bytes;
        src->bytes_in_buffer -= (size_t) num_bytes;
    }
}
 
static void qt_term_source(j_decompress_ptr cinfo)
{
    my_jpeg_source_mgr* src = (my_jpeg_source_mgr*)cinfo->src;
    if (!src->device->isSequential())
        src->device->seek(src->device->pos() - src->bytes_in_buffer);
}
 
}
 
inline my_jpeg_source_mgr::my_jpeg_source_mgr(QIODevice *device)
{
    jpeg_source_mgr::init_source = qt_init_source;
    jpeg_source_mgr::fill_input_buffer = qt_fill_input_buffer;
    jpeg_source_mgr::skip_input_data = qt_skip_input_data;
    jpeg_source_mgr::resync_to_restart = jpeg_resync_to_restart;
    jpeg_source_mgr::term_source = qt_term_source;
    this->device = device;
    memDevice = qobject_cast<QBuffer *>(device);
    bytes_in_buffer = 0;
    next_input_byte = buffer;
}
 
 
inline static bool read_jpeg_size(int &w, int &h, j_decompress_ptr cinfo)
{
    (void) jpeg_calc_output_dimensions(cinfo);
 
    w = cinfo->output_width;
    h = cinfo->output_height;
    return true;
}
 
#define HIGH_QUALITY_THRESHOLD 50
 
inline static bool read_jpeg_format(QImage::Format &format, j_decompress_ptr cinfo)
{
 
    bool result = true;
    switch (cinfo->output_components) {
    case 1:
        format = QImage::Format_Grayscale8;
        break;
    case 3:
        format = QImage::Format_RGB32;
        break;
    case 4:
        if (cinfo->out_color_space == JCS_CMYK)
            format = QImage::Format_CMYK8888;
        else
            format = QImage::Format_RGB32;
        break;
    default:
        result = false;
        break;
    }
    cinfo->output_scanline = cinfo->output_height;
    return result;
}
 
static bool ensureValidImage(QImage *dest, struct jpeg_decompress_struct *info,
                             const QSize& size)
{
    QImage::Format format;
    switch (info->output_components) {
    case 1:
        format = QImage::Format_Grayscale8;
        break;
    case 3:
        format = QImage::Format_RGB32;
        break;
    case 4:
        if (info->out_color_space == JCS_CMYK)
            format = QImage::Format_CMYK8888;
        else
            format = QImage::Format_RGB32;
        break;
    default:
        return false; // unsupported format
    }
 
    return QImageIOHandler::allocateImage(size, format, dest);
}
 
static bool read_jpeg_image(QImage *outImage,
                            QSize scaledSize, QRect scaledClipRect,
                            QRect clipRect, int quality,
                            Rgb888ToRgb32Converter converter,
                            j_decompress_ptr info, struct my_error_mgr* err, bool invertCMYK)
{
    if (!setjmp(err->setjmp_buffer)) {
        // -1 means default quality.
        if (quality < 0)
            quality = 75;
 
        // If possible, merge the scaledClipRect into either scaledSize
        // or clipRect to avoid doing a separate scaled clipping pass.
        // Best results are achieved by clipping before scaling, not after.
        if (!scaledClipRect.isEmpty()) {
            if (scaledSize.isEmpty() && clipRect.isEmpty()) {
                // No clipping or scaling before final clip.
                clipRect = scaledClipRect;
                scaledClipRect = QRect();
            } else if (scaledSize.isEmpty()) {
                // Clipping, but no scaling: combine the clip regions.
                scaledClipRect.translate(clipRect.topLeft());
                clipRect = scaledClipRect.intersected(clipRect);
                scaledClipRect = QRect();
            } else if (clipRect.isEmpty()) {
                // No clipping, but scaling: if we can map back to an
                // integer pixel boundary, then clip before scaling.
                if ((info->image_width % scaledSize.width()) == 0 &&
                        (info->image_height % scaledSize.height()) == 0) {
                    int x = scaledClipRect.x() * info->image_width /
                            scaledSize.width();
                    int y = scaledClipRect.y() * info->image_height /
                            scaledSize.height();
                    int width = (scaledClipRect.right() + 1) *
                                info->image_width / scaledSize.width() - x;
                    int height = (scaledClipRect.bottom() + 1) *
                                 info->image_height / scaledSize.height() - y;
                    clipRect = QRect(x, y, width, height);
                    scaledSize = scaledClipRect.size();
                    scaledClipRect = QRect();
                }
            } else {
                // Clipping and scaling: too difficult to figure out,
                // and not a likely use case, so do it the long way.
            }
        }
 
        // Determine the scale factor to pass to libjpeg for quick downscaling.
        if (!scaledSize.isEmpty() && info->image_width && info->image_height) {
            if (clipRect.isEmpty()) {
                double f = qMin(double(info->image_width) / scaledSize.width(),
                                double(info->image_height) / scaledSize.height());
 
                // libjpeg supports M/8 scaling with M=[1,16]. All downscaling factors
                // are a speed improvement, but upscaling during decode is slower.
                info->scale_num   = qBound(1, qCeil(8/f), 8);
                info->scale_denom = 8;
            } else {
                info->scale_denom = qMin(clipRect.width() / scaledSize.width(),
                                         clipRect.height() / scaledSize.height());
 
                // Only scale by powers of two when clipping so we can
                // keep the exact pixel boundaries
                if (info->scale_denom < 2)
                    info->scale_denom = 1;
                else if (info->scale_denom < 4)
                    info->scale_denom = 2;
                else if (info->scale_denom < 8)
                    info->scale_denom = 4;
                else
                    info->scale_denom = 8;
                info->scale_num = 1;
 
                // Correct the scale factor so that we clip accurately.
                // It is recommended that the clip rectangle be aligned
                // on an 8-pixel boundary for best performance.
                while (info->scale_denom > 1 &&
                       ((clipRect.x() % info->scale_denom) != 0 ||
                        (clipRect.y() % info->scale_denom) != 0 ||
                        (clipRect.width() % info->scale_denom) != 0 ||
                        (clipRect.height() % info->scale_denom) != 0)) {
                    info->scale_denom /= 2;
                }
            }
        }
 
        // If high quality not required, use fast decompression
        if ( quality < HIGH_QUALITY_THRESHOLD ) {
            info->dct_method = JDCT_IFAST;
            info->do_fancy_upsampling = FALSE;
        }
 
        (void) jpeg_calc_output_dimensions(info);
 
        // Determine the clip region to extract.
        QRect imageRect(0, 0, info->output_width, info->output_height);
        QRect clip;
        if (clipRect.isEmpty()) {
            clip = imageRect;
        } else if (info->scale_denom == info->scale_num) {
            clip = clipRect.intersected(imageRect);
        } else {
            // The scale factor was corrected above to ensure that
            // we don't miss pixels when we scale the clip rectangle.
            clip = QRect(clipRect.x() / int(info->scale_denom),
                         clipRect.y() / int(info->scale_denom),
                         clipRect.width() / int(info->scale_denom),
                         clipRect.height() / int(info->scale_denom));
            clip = clip.intersected(imageRect);
        }
 
        // Allocate memory for the clipped QImage.
        if (!ensureValidImage(outImage, info, clip.size()))
            return false;
 
        // Avoid memcpy() overhead if grayscale with no clipping.
        bool quickGray = (info->output_components == 1 &&
                          clip == imageRect);
        if (!quickGray) {
            // Ask the jpeg library to allocate a temporary row.
            // The library will automatically delete it for us later.
            // The libjpeg docs say we should do this before calling
            // jpeg_start_decompress().  We can't use "new" here
            // because we are inside the setjmp() block and an error
            // in the jpeg input stream would cause a memory leak.
            JSAMPARRAY rows = (info->mem->alloc_sarray)
                              ((j_common_ptr)info, JPOOL_IMAGE,
                               info->output_width * info->output_components, 1);
 
            (void) jpeg_start_decompress(info);
 
            while (info->output_scanline < info->output_height) {
                int y = int(info->output_scanline) - clip.y();
                if (y >= clip.height())
                    break;      // We've read the entire clip region, so abort.
 
                (void) jpeg_read_scanlines(info, rows, 1);
 
                if (y < 0)
                    continue;   // Haven't reached the starting line yet.
 
                if (info->output_components == 3) {
                    uchar *in = rows[0] + clip.x() * 3;
                    QRgb *out = (QRgb*)outImage->scanLine(y);
                    converter(out, in, clip.width());
                } else if (info->out_color_space == JCS_CMYK) {
                    uchar *in = rows[0] + clip.x() * 4;
                    quint32 *out = (quint32*)outImage->scanLine(y);
                    if (invertCMYK) {
                        for (int i = 0; i < clip.width(); ++i) {
                            *out++ = 0xffffffffu - (in[0] | in[1] << 8 | in[2] << 16 | in[3] << 24);
                            in += 4;
                        }
                    } else {
                        memcpy(out, in, clip.width() * 4);
                    }
                } else if (info->output_components == 1) {
                    // Grayscale.
                    memcpy(outImage->scanLine(y),
                           rows[0] + clip.x(), clip.width());
                }
            }
        } else {
            // Load unclipped grayscale data directly into the QImage.
            (void) jpeg_start_decompress(info);
            while (info->output_scanline < info->output_height) {
                uchar *row = outImage->scanLine(info->output_scanline);
                (void) jpeg_read_scanlines(info, &row, 1);
            }
        }
 
        if (info->output_scanline == info->output_height)
            (void) jpeg_finish_decompress(info);
 
        if (info->density_unit == 1) {
            outImage->setDotsPerMeterX(int(100. * info->X_density / 2.54));
            outImage->setDotsPerMeterY(int(100. * info->Y_density / 2.54));
        } else if (info->density_unit == 2) {
            outImage->setDotsPerMeterX(int(100. * info->X_density));
            outImage->setDotsPerMeterY(int(100. * info->Y_density));
        }
 
        if (scaledSize.isValid() && scaledSize != clip.size()) {
            *outImage = outImage->scaled(scaledSize, Qt::IgnoreAspectRatio, quality >= HIGH_QUALITY_THRESHOLD ? Qt::SmoothTransformation : Qt::FastTransformation);
        }
 
        if (!scaledClipRect.isEmpty())
            *outImage = outImage->copy(scaledClipRect);
        return !outImage->isNull();
    }
    else {
        my_output_message(j_common_ptr(info));
        return false;
    }
}
 
struct my_jpeg_destination_mgr : public jpeg_destination_mgr {
    // Nothing dynamic - cannot rely on destruction over longjump
    QIODevice *device;
    JOCTET buffer[max_buf];
 
public:
    my_jpeg_destination_mgr(QIODevice *);
};
 
 
extern "C" {
 
static void qt_init_destination(j_compress_ptr)
{
}
 
static boolean qt_empty_output_buffer(j_compress_ptr cinfo)
{
    my_jpeg_destination_mgr* dest = (my_jpeg_destination_mgr*)cinfo->dest;
 
    int written = dest->device->write((char*)dest->buffer, max_buf);
    if (written == -1)
        (*cinfo->err->error_exit)((j_common_ptr)cinfo);
 
    dest->next_output_byte = dest->buffer;
    dest->free_in_buffer = max_buf;
 
    return TRUE;
}
 
static void qt_term_destination(j_compress_ptr cinfo)
{
    my_jpeg_destination_mgr* dest = (my_jpeg_destination_mgr*)cinfo->dest;
    qint64 n = max_buf - dest->free_in_buffer;
 
    qint64 written = dest->device->write((char*)dest->buffer, n);
    if (written == -1)
        (*cinfo->err->error_exit)((j_common_ptr)cinfo);
}
 
}
 
inline my_jpeg_destination_mgr::my_jpeg_destination_mgr(QIODevice *device)
{
    jpeg_destination_mgr::init_destination = qt_init_destination;
    jpeg_destination_mgr::empty_output_buffer = qt_empty_output_buffer;
    jpeg_destination_mgr::term_destination = qt_term_destination;
    this->device = device;
    next_output_byte = buffer;
    free_in_buffer = max_buf;
}
 
static constexpr int maxMarkerSize = 65533;
 
static inline void set_text(const QImage &image, j_compress_ptr cinfo, const QString &description)
{
    const QMap<QString, QString> text = qt_getImageText(image, description);
    for (auto it = text.begin(), end = text.end(); it != end; ++it) {
        QByteArray comment = it.key().toUtf8();
        if (!comment.isEmpty())
            comment += ": ";
        comment += it.value().toUtf8();
        if (comment.size() > maxMarkerSize)
            comment.truncate(maxMarkerSize);
        jpeg_write_marker(cinfo, JPEG_COM, (const JOCTET *)comment.constData(), comment.size());
    }
}
 
static inline void write_icc_profile(const QImage &image, j_compress_ptr cinfo)
{
    const QByteArray iccProfile = image.colorSpace().iccProfile();
    if (iccProfile.isEmpty())
        return;
 
    const QByteArray iccSignature("ICC_PROFILE", 12);
    constexpr int maxIccMarkerSize = maxMarkerSize - (12 + 2);
    int index = 0;
    const int markers = (iccProfile.size() + (maxIccMarkerSize - 1)) / maxIccMarkerSize;
    Q_ASSERT(markers < 256);
    for (int marker = 1; marker <= markers; ++marker) {
        const int len = qMin(iccProfile.size() - index, maxIccMarkerSize);
        const QByteArray block = iccSignature
                               + QByteArray(1, char(marker)) + QByteArray(1, char(markers))
                               + iccProfile.mid(index, len);
        jpeg_write_marker(cinfo, JPEG_APP0 + 2, reinterpret_cast<const JOCTET *>(block.constData()), block.size());
        index += len;
    }
}
 
static bool do_write_jpeg_image(struct jpeg_compress_struct &cinfo,
                                JSAMPROW *row_pointer,
                                const QImage &image,
                                QIODevice *device,
                                int sourceQuality,
                                const QString &description,
                                bool optimize,
                                bool progressive,
                                bool invertCMYK)
{
    bool success = false;
    const QList<QRgb> cmap = image.colorTable();
 
    if (image.format() == QImage::Format_Invalid || image.format() == QImage::Format_Alpha8)
        return false;
 
    struct my_jpeg_destination_mgr *iod_dest = new my_jpeg_destination_mgr(device);
    struct my_error_mgr jerr;
 
    cinfo.err = jpeg_std_error(&jerr);
    jerr.error_exit = my_error_exit;
    jerr.output_message = my_output_message;
 
    if (!setjmp(jerr.setjmp_buffer)) {
        // WARNING:
        // this if loop is inside a setjmp/longjmp branch
        // do not create C++ temporaries here because the destructor may never be called
        // if you allocate memory, make sure that you can free it (row_pointer[0])
        jpeg_create_compress(&cinfo);
 
        cinfo.dest = iod_dest;
 
        cinfo.image_width = image.width();
        cinfo.image_height = image.height();
 
        bool gray = false;
        switch (image.format()) {
        case QImage::Format_Mono:
        case QImage::Format_MonoLSB:
        case QImage::Format_Indexed8:
            gray = true;
            for (int i = image.colorCount(); gray && i; i--) {
                gray = gray & qIsGray(cmap[i-1]);
            }
            cinfo.input_components = gray ? 1 : 3;
            cinfo.in_color_space = gray ? JCS_GRAYSCALE : JCS_RGB;
            break;
        case QImage::Format_Grayscale8:
        case QImage::Format_Grayscale16:
            gray = true;
            cinfo.input_components = 1;
            cinfo.in_color_space = JCS_GRAYSCALE;
            break;
        case QImage::Format_CMYK8888:
            cinfo.input_components = 4;
            cinfo.in_color_space = JCS_CMYK;
            break;
        default:
            cinfo.input_components = 3;
            cinfo.in_color_space = JCS_RGB;
        }
 
        jpeg_set_defaults(&cinfo);
 
        qreal diffInch = qAbs(image.dotsPerMeterX()*2.54/100. - qRound(image.dotsPerMeterX()*2.54/100.))
                         + qAbs(image.dotsPerMeterY()*2.54/100. - qRound(image.dotsPerMeterY()*2.54/100.));
        qreal diffCm = (qAbs(image.dotsPerMeterX()/100. - qRound(image.dotsPerMeterX()/100.))
                        + qAbs(image.dotsPerMeterY()/100. - qRound(image.dotsPerMeterY()/100.)))*2.54;
        if (diffInch < diffCm) {
            cinfo.density_unit = 1; // dots/inch
            cinfo.X_density = qRound(image.dotsPerMeterX()*2.54/100.);
            cinfo.Y_density = qRound(image.dotsPerMeterY()*2.54/100.);
        } else {
            cinfo.density_unit = 2; // dots/cm
            cinfo.X_density = (image.dotsPerMeterX()+50) / 100;
            cinfo.Y_density = (image.dotsPerMeterY()+50) / 100;
        }
 
        if (optimize)
            cinfo.optimize_coding = true;
 
        if (progressive)
            jpeg_simple_progression(&cinfo);
 
        int quality = sourceQuality >= 0 ? qMin(int(sourceQuality),100) : 75;
        jpeg_set_quality(&cinfo, quality, TRUE /* limit to baseline-JPEG values */);
 
        // If the quality exceeds a certain threshold (such as 90), disable chroma subsampling
        if (quality > 90) {
            cinfo.comp_info[0].v_samp_factor = 1;
            cinfo.comp_info[0].h_samp_factor = 1;
        }
 
        jpeg_start_compress(&cinfo, TRUE);
 
        set_text(image, &cinfo, description);
        if (cinfo.in_color_space == JCS_RGB || cinfo.in_color_space == JCS_CMYK)
            write_icc_profile(image, &cinfo);
 
        row_pointer[0] = new uchar[cinfo.image_width*cinfo.input_components];
        int w = cinfo.image_width;
        while (cinfo.next_scanline < cinfo.image_height) {
            uchar *row = row_pointer[0];
            switch (image.format()) {
            case QImage::Format_Mono:
            case QImage::Format_MonoLSB:
                if (gray) {
                    const uchar* data = image.constScanLine(cinfo.next_scanline);
                    if (image.format() == QImage::Format_MonoLSB) {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (i & 7)));
                            row[i] = qRed(cmap[bit]);
                        }
                    } else {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (7 -(i & 7))));
                            row[i] = qRed(cmap[bit]);
                        }
                    }
                } else {
                    const uchar* data = image.constScanLine(cinfo.next_scanline);
                    if (image.format() == QImage::Format_MonoLSB) {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (i & 7)));
                            *row++ = qRed(cmap[bit]);
                            *row++ = qGreen(cmap[bit]);
                            *row++ = qBlue(cmap[bit]);
                        }
                    } else {
                        for (int i=0; i<w; i++) {
                            bool bit = !!(*(data + (i >> 3)) & (1 << (7 -(i & 7))));
                            *row++ = qRed(cmap[bit]);
                            *row++ = qGreen(cmap[bit]);
                            *row++ = qBlue(cmap[bit]);
                        }
                    }
                }
                break;
            case QImage::Format_Indexed8:
                if (gray) {
                    const uchar* pix = image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row = qRed(cmap[*pix]);
                        ++row; ++pix;
                    }
                } else {
                    const uchar* pix = image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(cmap[*pix]);
                        *row++ = qGreen(cmap[*pix]);
                        *row++ = qBlue(cmap[*pix]);
                        ++pix;
                    }
                }
                break;
            case QImage::Format_Grayscale8:
                memcpy(row, image.constScanLine(cinfo.next_scanline), w);
                break;
            case QImage::Format_Grayscale16:
                {
                    QImage rowImg = image.copy(0, cinfo.next_scanline, w, 1).convertToFormat(QImage::Format_Grayscale8);
                    memcpy(row, rowImg.constScanLine(0), w);
                }
                break;
            case QImage::Format_RGB888:
                memcpy(row, image.constScanLine(cinfo.next_scanline), w * 3);
                break;
            case QImage::Format_RGB32:
            case QImage::Format_ARGB32:
            case QImage::Format_ARGB32_Premultiplied:
                {
                    const QRgb* rgb = (const QRgb*)image.constScanLine(cinfo.next_scanline);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(*rgb);
                        *row++ = qGreen(*rgb);
                        *row++ = qBlue(*rgb);
                        ++rgb;
                    }
                }
                break;
            case QImage::Format_CMYK8888: {
                auto *cmykIn = reinterpret_cast<const quint32 *>(image.constScanLine(cinfo.next_scanline));
                auto *cmykOut = reinterpret_cast<quint32 *>(row);
                if (invertCMYK) {
                    for (int i = 0; i < w; ++i)
                        cmykOut[i] = 0xffffffffu - cmykIn[i];
                } else {
                    memcpy(cmykOut, cmykIn, w * 4);
                }
                break;
            }
            default:
                {
                    // (Testing shows that this way is actually faster than converting to RGB888 + memcpy)
                    QImage rowImg = image.copy(0, cinfo.next_scanline, w, 1).convertToFormat(QImage::Format_RGB32);
                    const QRgb* rgb = (const QRgb*)rowImg.constScanLine(0);
                    for (int i=0; i<w; i++) {
                        *row++ = qRed(*rgb);
                        *row++ = qGreen(*rgb);
                        *row++ = qBlue(*rgb);
                        ++rgb;
                    }
                }
                break;
            }
            jpeg_write_scanlines(&cinfo, row_pointer, 1);
        }
 
        jpeg_finish_compress(&cinfo);
        jpeg_destroy_compress(&cinfo);
        success = true;
    } else {
        my_output_message(j_common_ptr(&cinfo));
        jpeg_destroy_compress(&cinfo);
        success = false;
    }
 
    delete iod_dest;
    return success;
}
 
static bool write_jpeg_image(const QImage &image,
                             QIODevice *device,
                             int sourceQuality,
                             const QString &description,
                             bool optimize,
                             bool progressive,
                             bool invertCMYK)
{
    // protect these objects from the setjmp/longjmp pair inside
    // do_write_jpeg_image (by making them non-local).
    struct jpeg_compress_struct cinfo;
    JSAMPROW row_pointer[1];
    row_pointer[0] = nullptr;
 
    const bool success = do_write_jpeg_image(cinfo, row_pointer,
                                             image, device,
                                             sourceQuality, description,
                                             optimize, progressive, invertCMYK);
 
    delete [] row_pointer[0];
    return success;
}
 
class QJpegHandlerPrivate
{
public:
    enum State {
        Ready,
        ReadHeader,
        ReadingEnd,
        Error
    };
 
    QJpegHandlerPrivate(QJpegHandler *qq)
        : quality(75), transformation(QImageIOHandler::TransformationNone), iod_src(nullptr),
          rgb888ToRgb32ConverterPtr(qt_convert_rgb888_to_rgb32), state(Ready), optimize(false), progressive(false), q(qq)
    {}
 
    ~QJpegHandlerPrivate()
    {
        if (iod_src)
        {
            jpeg_destroy_decompress(&info);
            delete iod_src;
            iod_src = nullptr;
        }
    }
 
    bool readJpegHeader(QIODevice*);
    bool read(QImage *image);
 
    int quality;
    QImageIOHandler::Transformations transformation;
    QVariant size;
    QImage::Format format;
    QSize scaledSize;
    QRect scaledClipRect;
    QRect clipRect;
    QString description;
    QStringList readTexts;
    QByteArray iccProfile;
 
    // Photoshop historically invertes the quantities in CMYK JPEG files:
    // 0 means 100% ink, 255 means no ink. Every reader does the same,
    // for compatibility reasons.
    // Use such an interpretation by default, but also offer the alternative
    // of not inverting the channels.
    // This is just a "fancy" API; it could be reduced to a boolean setting
    // for CMYK files.
    enum class SubType {
        Automatic,
        Inverted_CMYK,
        CMYK,
        NSubTypes
    };
    SubType subType = SubType::Automatic;
 
    struct jpeg_decompress_struct info;
    struct my_jpeg_source_mgr * iod_src;
    struct my_error_mgr err;
 
    Rgb888ToRgb32Converter rgb888ToRgb32ConverterPtr;
 
    State state;
 
    bool optimize;
    bool progressive;
 
    QJpegHandler *q;
};
 
static const char SupportedJPEGSubtypes[][14] = {
    "Automatic",
    "Inverted_CMYK",
    "CMYK"
};
 
static_assert(std::size(SupportedJPEGSubtypes) == size_t(QJpegHandlerPrivate::SubType::NSubTypes));
 
static bool readExifHeader(QDataStream &stream)
{
    char prefix[6];
    if (stream.readRawData(prefix, sizeof(prefix)) != sizeof(prefix))
        return false;
    static const char exifMagic[6] = {'E', 'x', 'i', 'f', 0, 0};
    return memcmp(prefix, exifMagic, 6) == 0;
}
 
/*
 * Returns -1 on error
 * Returns 0 if no Exif orientation was found
 * Returns 1 orientation is horizontal (normal)
 * Returns 2 mirror horizontal
 * Returns 3 rotate 180
 * Returns 4 mirror vertical
 * Returns 5 mirror horizontal and rotate 270 CCW
 * Returns 6 rotate 90 CW
 * Returns 7 mirror horizontal and rotate 90 CW
 * Returns 8 rotate 270 CW
 */
static int getExifOrientation(QByteArray &exifData)
{
    // Current EXIF version (2.3) says there can be at most 5 IFDs,
    // byte we allow for 10 so we're able to deal with future extensions.
    const int maxIfdCount = 10;
 
    QDataStream stream(&exifData, QIODevice::ReadOnly);
 
    if (!readExifHeader(stream))
        return -1;
 
    quint16 val;
    quint32 offset;
    const qint64 headerStart = 6;   // the EXIF header has a constant size
    Q_ASSERT(headerStart == stream.device()->pos());
 
    // read byte order marker
    stream >> val;
    if (val == 0x4949) // 'II' == Intel
        stream.setByteOrder(QDataStream::LittleEndian);
    else if (val == 0x4d4d) // 'MM' == Motorola
        stream.setByteOrder(QDataStream::BigEndian);
    else
        return -1; // unknown byte order
 
    // confirm byte order
    stream >> val;
    if (val != 0x2a)
        return -1;
 
    stream >> offset;
 
    // read IFD
    for (int n = 0; n < maxIfdCount; ++n) {
        quint16 numEntries;
 
        const qint64 bytesToSkip = offset - (stream.device()->pos() - headerStart);
        if (bytesToSkip < 0 || (offset + headerStart >= exifData.size())) {
            // disallow going backwards, though it's permitted in the spec
            return -1;
        } else if (bytesToSkip != 0) {
            // seek to the IFD
            if (!stream.device()->seek(offset + headerStart))
                return -1;
        }
 
        stream >> numEntries;
 
        for (; numEntries > 0 && stream.status() == QDataStream::Ok; --numEntries) {
            quint16 tag;
            quint16 type;
            quint32 components;
            quint16 value;
            quint16 dummy;
 
            stream >> tag >> type >> components >> value >> dummy;
            if (tag == 0x0112) { // Tag Exif.Image.Orientation
                if (components != 1)
                    return -1;
                if (type != 3) // we are expecting it to be an unsigned short
                    return -1;
                if (value < 1 || value > 8) // check for valid range
                    return -1;
 
                // It is possible to include the orientation multiple times.
                // Right now the first value is returned.
                return value;
            }
        }
 
        // read offset to next IFD
        if (!(stream >> offset))
            return -1;
        if (offset == 0) // this is the last IFD
            return 0;   // No Exif orientation was found
    }
 
    // too many IFDs
    return -1;
}
 
static QImageIOHandler::Transformations exif2Qt(int exifOrientation)
{
    switch (exifOrientation) {
    case 1: // normal
        return QImageIOHandler::TransformationNone;
    case 2: // mirror horizontal
        return QImageIOHandler::TransformationMirror;
    case 3: // rotate 180
        return QImageIOHandler::TransformationRotate180;
    case 4: // mirror vertical
        return QImageIOHandler::TransformationFlip;
    case 5: // mirror horizontal and rotate 270 CW
        return QImageIOHandler::TransformationFlipAndRotate90;
    case 6: // rotate 90 CW
        return QImageIOHandler::TransformationRotate90;
    case 7: // mirror horizontal and rotate 90 CW
        return QImageIOHandler::TransformationMirrorAndRotate90;
    case 8: // rotate 270 CW
        return QImageIOHandler::TransformationRotate270;
    }
    qCWarning(lcJpeg, "Invalid EXIF orientation");
    return QImageIOHandler::TransformationNone;
}
 
/*!
    \internal
*/
bool QJpegHandlerPrivate::readJpegHeader(QIODevice *device)
{
    if (state == Ready)
    {
        state = Error;
        iod_src = new my_jpeg_source_mgr(device);
 
        info.err = jpeg_std_error(&err);
        err.error_exit = my_error_exit;
        err.output_message = my_output_message;
 
        jpeg_create_decompress(&info);
        info.src = iod_src;
        if (const int mbLimit = QImageReader::allocationLimit()) {
            const qint64 bMax = 2 * qint64(mbLimit) * 1024 * 1024; // Some overhead for temp alloc
            info.mem->max_memory_to_use = long(qMin(bMax, qint64(std::numeric_limits<long>::max())));
        }
 
        if (!setjmp(err.setjmp_buffer)) {
            jpeg_save_markers(&info, JPEG_COM, 0xFFFF);
            jpeg_save_markers(&info, JPEG_APP0 + 1, 0xFFFF); // Exif uses APP1 marker
            jpeg_save_markers(&info, JPEG_APP0 + 2, 0xFFFF); // ICC uses APP2 marker
 
            (void) jpeg_read_header(&info, TRUE);
 
            int width = 0;
            int height = 0;
            read_jpeg_size(width, height, &info);
            size = QSize(width, height);
 
            format = QImage::Format_Invalid;
            read_jpeg_format(format, &info);
 
            QByteArray exifData;
 
            for (jpeg_saved_marker_ptr marker = info.marker_list; marker != nullptr; marker = marker->next) {
                if (marker->marker == JPEG_COM) {
#ifndef QT_NO_IMAGEIO_TEXT_LOADING
                    QString key, value;
                    QString s = QString::fromUtf8((const char *)marker->data, marker->data_length);
                    int index = s.indexOf(QLatin1String(": "));
                    if (index == -1 || s.indexOf(QLatin1Char(' ')) < index) {
                        key = QLatin1String("Description");
                        value = s;
                    } else {
                        key = s.left(index);
                        value = s.mid(index + 2);
                    }
                    if (!description.isEmpty())
                        description += QLatin1String("\n\n");
                    description += key + QLatin1String(": ") + value.simplified();
                    readTexts.append(key);
                    readTexts.append(value);
#endif
                } else if (marker->marker == JPEG_APP0 + 1) {
                    exifData.append((const char*)marker->data, marker->data_length);
                } else if (marker->marker == JPEG_APP0 + 2) {
                    if (marker->data_length > 128 + 4 + 14 && strcmp((const char *)marker->data, "ICC_PROFILE") == 0) {
                        iccProfile.append((const char*)marker->data + 14, marker->data_length - 14);
                    }
                }
            }
 
            if (!exifData.isEmpty()) {
                // Exif data present
                int exifOrientation = getExifOrientation(exifData);
                if (exifOrientation > 0)
                    transformation = exif2Qt(exifOrientation);
            }
 
            state = ReadHeader;
            return true;
        }
        else {
            my_output_message(j_common_ptr(&info));
            return false;
        }
    }
    else if (state == Error)
        return false;
    return true;
}
 
bool QJpegHandlerPrivate::read(QImage *image)
{
    if (state == Ready)
        readJpegHeader(q->device());
 
    if (state == ReadHeader)
    {
        const bool invertCMYK = subType != QJpegHandlerPrivate::SubType::CMYK;
        bool success = read_jpeg_image(image, scaledSize, scaledClipRect, clipRect, quality, rgb888ToRgb32ConverterPtr, &info, &err, invertCMYK);
        if (success) {
            for (int i = 0; i < readTexts.size()-1; i+=2)
                image->setText(readTexts.at(i), readTexts.at(i+1));
 
            if (!iccProfile.isEmpty())
                image->setColorSpace(QColorSpace::fromIccProfile(iccProfile));
 
            state = ReadingEnd;
            return true;
        }
 
        state = Error;
    }
 
    return false;
}
 
Q_GUI_EXPORT void QT_FASTCALL qt_convert_rgb888_to_rgb32_neon(quint32 *dst, const uchar *src, int len);
Q_GUI_EXPORT void QT_FASTCALL qt_convert_rgb888_to_rgb32_ssse3(quint32 *dst, const uchar *src, int len);
extern "C" void qt_convert_rgb888_to_rgb32_mips_dspr2_asm(quint32 *dst, const uchar *src, int len);
 
QJpegHandler::QJpegHandler()
    : d(new QJpegHandlerPrivate(this))
{
#if defined(__ARM_NEON__)
    // from qimage_neon.cpp
    if (qCpuHasFeature(NEON))
        d->rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_neon;
#endif
 
#if defined(QT_COMPILER_SUPPORTS_SSSE3)
    // from qimage_ssse3.cpps
    if (qCpuHasFeature(SSSE3)) {
        d->rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_ssse3;
    }
#endif // QT_COMPILER_SUPPORTS_SSSE3
#if defined(QT_COMPILER_SUPPORTS_MIPS_DSPR2)
    if (qCpuHasFeature(DSPR2)) {
        d->rgb888ToRgb32ConverterPtr = qt_convert_rgb888_to_rgb32_mips_dspr2_asm;
    }
#endif // QT_COMPILER_SUPPORTS_DSPR2
}
 
QJpegHandler::~QJpegHandler()
{
    delete d;
}
 
bool QJpegHandler::canRead() const
{
    if (d->state == QJpegHandlerPrivate::Ready && !canRead(device()))
        return false;
 
    if (d->state != QJpegHandlerPrivate::Error && d->state != QJpegHandlerPrivate::ReadingEnd) {
        setFormat("jpeg");
        return true;
    }
 
    return false;
}
 
bool QJpegHandler::canRead(QIODevice *device)
{
    if (!device) {
        qCWarning(lcJpeg, "QJpegHandler::canRead() called with no device");
        return false;
    }
 
    char buffer[2];
    if (device->peek(buffer, 2) != 2)
        return false;
    return uchar(buffer[0]) == 0xff && uchar(buffer[1]) == 0xd8;
}
 
bool QJpegHandler::read(QImage *image)
{
    if (!canRead())
        return false;
    return d->read(image);
}
 
extern void qt_imageTransform(QImage &src, QImageIOHandler::Transformations orient);
 
bool QJpegHandler::write(const QImage &image)
{
    const bool invertCMYK = d->subType != QJpegHandlerPrivate::SubType::CMYK;
    if (d->transformation != QImageIOHandler::TransformationNone) {
        // We don't support writing EXIF headers so apply the transform to the data.
        QImage img = image;
        qt_imageTransform(img, d->transformation);
        return write_jpeg_image(img, device(), d->quality, d->description, d->optimize, d->progressive, invertCMYK);
    }
    return write_jpeg_image(image, device(), d->quality, d->description, d->optimize, d->progressive, invertCMYK);
}
 
bool QJpegHandler::supportsOption(ImageOption option) const
{
    return option == Quality
        || option == ScaledSize
        || option == ScaledClipRect
        || option == ClipRect
        || option == Description
        || option == Size
        || option == SubType
        || option == SupportedSubTypes
        || option == ImageFormat
        || option == OptimizedWrite
        || option == ProgressiveScanWrite
        || option == ImageTransformation;
}
 
QVariant QJpegHandler::option(ImageOption option) const
{
    switch(option) {
    case Quality:
        return d->quality;
    case ScaledSize:
        return d->scaledSize;
    case ScaledClipRect:
        return d->scaledClipRect;
    case ClipRect:
        return d->clipRect;
    case Description:
        d->readJpegHeader(device());
        return d->description;
    case Size:
        d->readJpegHeader(device());
        return d->size;
    case SubType:
        return QByteArray(SupportedJPEGSubtypes[int(d->subType)]);
    case SupportedSubTypes: {
        QByteArrayList list(std::begin(SupportedJPEGSubtypes),
                            std::end(SupportedJPEGSubtypes));
        return QVariant::fromValue(list);
    }
    case ImageFormat:
        d->readJpegHeader(device());
        return d->format;
    case OptimizedWrite:
        return d->optimize;
    case ProgressiveScanWrite:
        return d->progressive;
    case ImageTransformation:
        d->readJpegHeader(device());
        return int(d->transformation);
    default:
        break;
    }
 
    return QVariant();
}
 
void QJpegHandler::setOption(ImageOption option, const QVariant &value)
{
    switch(option) {
    case Quality:
        d->quality = value.toInt();
        break;
    case ScaledSize:
        d->scaledSize = value.toSize();
        break;
    case ScaledClipRect:
        d->scaledClipRect = value.toRect();
        break;
    case ClipRect:
        d->clipRect = value.toRect();
        break;
    case Description:
        d->description = value.toString();
        break;
    case SubType: {
        const QByteArray subType = value.toByteArray();
        for (size_t i = 0; i < std::size(SupportedJPEGSubtypes); ++i) {
            if (subType == SupportedJPEGSubtypes[i]) {
                d->subType = QJpegHandlerPrivate::SubType(i);
                break;
            }
        }
        break;
    }
    case OptimizedWrite:
        d->optimize = value.toBool();
        break;
    case ProgressiveScanWrite:
        d->progressive = value.toBool();
        break;
    case ImageTransformation: {
        int transformation = value.toInt();
        if (transformation > 0 && transformation < 8)
            d->transformation = QImageIOHandler::Transformations(transformation);
        break;
    }
    default:
        break;
    }
}
 
QT_END_NAMESPACE