Always build JPEG and GIF support as plugins

Our handling of plugins when Qt is build statically is
nowadays good enough, so we don't need to build the
JPEG and GIF support directly into Qt for static builds.
Let's simply always build them as plugins.

Also simplify the logic in configure, and get rid of the
no-gif, no-jpeg and no-png config variables.

[ChangelLog][Build system] JPEG and GIF image support is now
always built as a plugin. Removed -imageformat-[jpeg|gif]
arguments to configure.

Change-Id: Ic01559ff406c966807b3be8761252e8802adcdf7
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>

3 files changed, 1240 insertions, 5 deletions

diff --git a/src/plugins/imageformats/jpeg/jpeg.pro b/src/plugins/imageformats/jpeg/jpeg.pro
index 526556179c..9181abb465 100644
--- a/src/plugins/imageformats/jpeg/jpeg.pro
+++ b/src/plugins/imageformats/jpeg/jpeg.pro
@@ -2,12 +2,18 @@ TARGET  = qjpeg
 
 QT += core-private
 
-QTDIR_build:REQUIRES = "!contains(QT_CONFIG, no-jpeg)"
+SOURCES += main.cpp qjpeghandler.cpp
+HEADERS += main.h qjpeghandler_p.h
+
+contains(QT_CONFIG, system-jpeg) {
+    msvc: \
+        LIBS += libjpeg.lib
+    else: \
+        LIBS += -ljpeg
+} else {
+    include($$PWD/../../../3rdparty/libjpeg.pri)
+}
 
-include(../../../gui/image/qjpeghandler.pri)
-INCLUDEPATH += ../../../gui/image
-SOURCES += main.cpp
-HEADERS += main.h
 OTHER_FILES += jpeg.json
 
 PLUGIN_TYPE = imageformats
diff --git a/src/plugins/imageformats/jpeg/qjpeghandler.cpp b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
new file mode 100644
index 0000000000..52e8b39f11
--- /dev/null
+++ b/src/plugins/imageformats/jpeg/qjpeghandler.cpp
@@ -0,0 +1,1144 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qjpeghandler_p.h"
+
+#include <qimage.h>
+#include <qvariant.h>
+#include <qvector.h>
+#include <qbuffer.h>
+#include <qmath.h>
+#include <private/qsimd_p.h>
+
+#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" {
+// mingw includes rpcndr.h but does not define boolean
+#if defined(Q_OS_WIN) && defined(Q_CC_GNU)
+#   if defined(__RPCNDR_H__) && !defined(boolean)
+        typedef unsigned char boolean;
+#       define HAVE_BOOLEAN
+#   endif
+#endif
+
+#define XMD_H           // shut JPEGlib up
+#if defined(Q_OS_UNIXWARE)
+#  define HAVE_BOOLEAN  // libjpeg under Unixware seems to need this
+#endif
+#include <jpeglib.h>
+#ifdef const
+#  undef const          // remove crazy C hackery in jconfig.h
+#endif
+}
+
+QT_BEGIN_NAMESPACE
+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)
+{
+    my_error_mgr* myerr = (my_error_mgr*) cinfo->err;
+    char buffer[JMSG_LENGTH_MAX];
+    (*cinfo->err->format_message)(cinfo, buffer);
+    qWarning("%s", buffer);
+    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);
+    qWarning("%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:
+    case 4:
+        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:
+    case 4:
+        format = QImage::Format_RGB32;
+        break;
+    default:
+        return false; // unsupported format
+    }
+
+    if (dest->size() != size || dest->format() != format)
+        *dest = QImage(size, format);
+
+    return !dest->isNull();
+}
+
+static bool read_jpeg_image(QImage *outImage,
+                            QSize scaledSize, QRect scaledClipRect,
+                            QRect clipRect, volatile int inQuality,
+                            Rgb888ToRgb32Converter converter,
+                            j_decompress_ptr info, struct my_error_mgr* err  )
+{
+    if (!setjmp(err->setjmp_buffer)) {
+        // -1 means default quality.
+        int quality = inQuality;
+        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()))
+            longjmp(err->setjmp_buffer, 1);
+
+        // 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) {
+                    // Convert CMYK->RGB.
+                    uchar *in = rows[0] + clip.x() * 4;
+                    QRgb *out = (QRgb*)outImage->scanLine(y);
+                    for (int i = 0; i < clip.width(); ++i) {
+                        int k = in[3];
+                        *out++ = qRgb(k * in[0] / 255, k * in[1] / 255,
+                                      k * in[2] / 255);
+                        in += 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
+        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 inline void set_text(const QImage &image, j_compress_ptr cinfo, const QString &description)
+{
+    QMap<QString, QString> text;
+    foreach (const QString &key, image.textKeys()) {
+        if (!key.isEmpty())
+            text.insert(key, image.text(key));
+    }
+    foreach (const QString &pair, description.split(QLatin1String("\n\n"))) {
+        int index = pair.indexOf(QLatin1Char(':'));
+        if (index >= 0 && pair.indexOf(QLatin1Char(' ')) < index) {
+            QString s = pair.simplified();
+            if (!s.isEmpty())
+                text.insert(QLatin1String("Description"), s);
+        } else {
+            QString key = pair.left(index);
+            if (!key.simplified().isEmpty())
+                text.insert(key, pair.mid(index + 2).simplified());
+        }
+    }
+    if (text.isEmpty())
+        return;
+
+    for (QMap<QString, QString>::ConstIterator it = text.constBegin(); it != text.constEnd(); ++it) {
+        QByteArray comment = it.key().toLatin1();
+        if (!comment.isEmpty())
+            comment += ": ";
+        comment += it.value().toLatin1();
+        if (comment.length() > 65530)
+            comment.truncate(65530);
+        jpeg_write_marker(cinfo, JPEG_COM, (const JOCTET *)comment.constData(), comment.size());
+    }
+}
+
+static bool write_jpeg_image(const QImage &image, QIODevice *device, volatile int sourceQuality, const QString &description, bool optimize, bool progressive)
+{
+    bool success = false;
+    const QVector<QRgb> cmap = image.colorTable();
+
+    if (image.format() == QImage::Format_Invalid || image.format() == QImage::Format_Alpha8)
+        return false;
+
+    struct jpeg_compress_struct cinfo;
+    JSAMPROW row_pointer[1];
+    row_pointer[0] = 0;
+
+    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:
+            gray = true;
+            cinfo.input_components = 1;
+            cinfo.in_color_space = JCS_GRAYSCALE;
+            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 */);
+        jpeg_start_compress(&cinfo, TRUE);
+
+        set_text(image, &cinfo, description);
+
+        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_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;
+            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 {
+        jpeg_destroy_compress(&cinfo);
+        success = false;
+    }
+
+    delete iod_dest;
+    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(0),
+          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 = 0;
+        }
+    }
+
+    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;
+
+    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 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)
+{
+    QDataStream stream(&exifData, QIODevice::ReadOnly);
+
+    if (!readExifHeader(stream))
+        return -1;
+
+    quint16 val;
+    quint32 offset;
+    const qint64 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
+
+    // read size
+    stream >> val;
+    if (val != 0x2a)
+        return -1;
+
+    stream >> offset;
+
+    // read IFD
+    while (!stream.atEnd()) {
+        quint16 numEntries;
+
+        // skip offset bytes to get the next IFD
+        const qint64 bytesToSkip = offset - (stream.device()->pos() - headerStart);
+
+        if (stream.skipRawData(bytesToSkip) != bytesToSkip)
+            return -1;
+
+        stream >> numEntries;
+
+        for (; numEntries > 0; --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
+        stream >> offset;
+        if (offset == 0) // this is the last IFD
+            break;
+    }
+
+    // No Exif orientation was found
+    return 0;
+}
+
+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;
+    }
+    qWarning("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 (!setjmp(err.setjmp_buffer)) {
+            jpeg_save_markers(&info, JPEG_COM, 0xFFFF);
+            jpeg_save_markers(&info, JPEG_APP0 + 1, 0xFFFF); // Exif uses APP1 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 != NULL; marker = marker->next) {
+                if (marker->marker == JPEG_COM) {
+                    QString key, value;
+                    QString s = QString::fromLatin1((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);
+                } else if (marker->marker == JPEG_APP0 + 1) {
+                    exifData.append((const char*)marker->data, marker->data_length);
+                }
+            }
+
+            if (!exifData.isEmpty()) {
+                // Exif data present
+                int exifOrientation = getExifOrientation(exifData);
+                if (exifOrientation > 0)
+                    transformation = exif2Qt(exifOrientation);
+            }
+
+            state = ReadHeader;
+            return true;
+        }
+        else
+        {
+            return false;
+        }
+    }
+    else if(state == Error)
+        return false;
+    return true;
+}
+
+bool QJpegHandlerPrivate::read(QImage *image)
+{
+    if(state == Ready)
+        readJpegHeader(q->device());
+
+    if(state == ReadHeader)
+    {
+        bool success = read_jpeg_image(image, scaledSize, scaledClipRect, clipRect, quality, rgb888ToRgb32ConverterPtr, &info, &err);
+        if (success) {
+            for (int i = 0; i < readTexts.size()-1; i+=2)
+                image->setText(readTexts.at(i), readTexts.at(i+1));
+
+            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) {
+        qWarning("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)
+{
+    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);
+    }
+    return write_jpeg_image(image, device(), d->quality, d->description, d->optimize, d->progressive);
+}
+
+bool QJpegHandler::supportsOption(ImageOption option) const
+{
+    return option == Quality
+        || option == ScaledSize
+        || option == ScaledClipRect
+        || option == ClipRect
+        || option == Description
+        || option == Size
+        || 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 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 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);
+    }
+    default:
+        break;
+    }
+}
+
+QByteArray QJpegHandler::name() const
+{
+    return "jpeg";
+}
+
+QT_END_NAMESPACE
diff --git a/src/plugins/imageformats/jpeg/qjpeghandler_p.h b/src/plugins/imageformats/jpeg/qjpeghandler_p.h
new file mode 100644
index 0000000000..534ce12115
--- /dev/null
+++ b/src/plugins/imageformats/jpeg/qjpeghandler_p.h
@@ -0,0 +1,85 @@
+/****************************************************************************
+**
+** Copyright (C) 2016 The Qt Company Ltd.
+** Contact: https://www.qt.io/licensing/
+**
+** This file is part of the plugins of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL$
+** Commercial License Usage
+** Licensees holding valid commercial Qt licenses may use this file in
+** accordance with the commercial license agreement provided with the
+** Software or, alternatively, in accordance with the terms contained in
+** a written agreement between you and The Qt Company. For licensing terms
+** and conditions see https://www.qt.io/terms-conditions. For further
+** information use the contact form at https://www.qt.io/contact-us.
+**
+** GNU Lesser General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU Lesser
+** General Public License version 3 as published by the Free Software
+** Foundation and appearing in the file LICENSE.LGPL3 included in the
+** packaging of this file. Please review the following information to
+** ensure the GNU Lesser General Public License version 3 requirements
+** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
+**
+** GNU General Public License Usage
+** Alternatively, this file may be used under the terms of the GNU
+** General Public License version 2.0 or (at your option) the GNU General
+** Public license version 3 or any later version approved by the KDE Free
+** Qt Foundation. The licenses are as published by the Free Software
+** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
+** included in the packaging of this file. Please review the following
+** information to ensure the GNU General Public License requirements will
+** be met: https://www.gnu.org/licenses/gpl-2.0.html and
+** https://www.gnu.org/licenses/gpl-3.0.html.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef QJPEGHANDLER_P_H
+#define QJPEGHANDLER_P_H
+
+//
+//  W A R N I N G
+//  -------------
+//
+// This file is not part of the Qt API.  It exists purely as an
+// implementation detail.  This header file may change from version to
+// version without notice, or even be removed.
+//
+// We mean it.
+//
+
+#include <QtGui/qimageiohandler.h>
+#include <QtCore/QSize>
+#include <QtCore/QRect>
+
+QT_BEGIN_NAMESPACE
+
+class QJpegHandlerPrivate;
+class QJpegHandler : public QImageIOHandler
+{
+public:
+    QJpegHandler();
+    ~QJpegHandler();
+
+    bool canRead() const Q_DECL_OVERRIDE;
+    bool read(QImage *image) Q_DECL_OVERRIDE;
+    bool write(const QImage &image) Q_DECL_OVERRIDE;
+
+    QByteArray name() const Q_DECL_OVERRIDE;
+
+    static bool canRead(QIODevice *device);
+
+    QVariant option(ImageOption option) const Q_DECL_OVERRIDE;
+    void setOption(ImageOption option, const QVariant &value) Q_DECL_OVERRIDE;
+    bool supportsOption(ImageOption option) const Q_DECL_OVERRIDE;
+
+private:
+    QJpegHandlerPrivate *d;
+};
+
+QT_END_NAMESPACE
+
+#endif // QJPEGHANDLER_P_H