Darwin: Add QImage::toCGImage() conversion function

(Move QT_FORWARD_DECLARE_CG to qglobal.h)

This function converts to CGImage for supported formats. This
is done by creating a CGImageRef that reuses the QImage data.

The CGImage and QImage ref counting systems are bridged, implemented
by using CGDataProvider that holds a copy of the QImage.

Unlike the previous internal implementation this public version
does not implicitly convert unsupported formats to ARGB32_Premultiplied.

See included documentation for the complete description.

Change-Id: Ie3984a7a8331e02a6f1c42943caaf76854e93538
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>
Reviewed-by: Gabriel de Dietrich <gabriel.dedietrich@qt.io>

src/corelib/global/qglobal.h

@@ -538,6 +538,12 @@ Q_DECL_CONSTEXPR inline const T &qBound(const T &min, const T &val, const T &max
 #ifndef Q_FORWARD_DECLARE_MUTABLE_CF_TYPE
 #  define Q_FORWARD_DECLARE_MUTABLE_CF_TYPE(type) typedef struct __ ## type * type ## Ref
 #endif
+#ifndef Q_FORWARD_DECLARE_CG_TYPE
+#define Q_FORWARD_DECLARE_CG_TYPE(type) typedef const struct type *type ## Ref;
+#endif
+#ifndef Q_FORWARD_DECLARE_MUTABLE_CG_TYPE
+#define Q_FORWARD_DECLARE_MUTABLE_CG_TYPE(type) typedef struct type *type ## Ref;
+#endif
 
 #ifdef Q_OS_DARWIN
 #  define QT_DARWIN_PLATFORM_SDK_EQUAL_OR_ABOVE(macos, ios, tvos, watchos) \

src/corelib/io/qdebug.h

@@ -438,8 +438,8 @@ inline QDebug operator<<(QDebug debug, const QFlags<T> &flags)
 
 #define QT_FORWARD_DECLARE_CF_TYPE(type) Q_FORWARD_DECLARE_CF_TYPE(type);
 #define QT_FORWARD_DECLARE_MUTABLE_CF_TYPE(type) Q_FORWARD_DECLARE_MUTABLE_CF_TYPE(type);
-#define QT_FORWARD_DECLARE_CG_TYPE(type) typedef const struct type *type ## Ref;
-#define QT_FORWARD_DECLARE_MUTABLE_CG_TYPE(type) typedef struct type *type ## Ref;
+#define QT_FORWARD_DECLARE_CG_TYPE(type) Q_FORWARD_DECLARE_CG_TYPE(type);
+#define QT_FORWARD_DECLARE_MUTABLE_CG_TYPE(type) Q_FORWARD_DECLARE_MUTABLE_CG_TYPE(type);
 
 QT_END_NAMESPACE
 Q_FORWARD_DECLARE_CF_TYPE(CFString);

src/gui/image/image.pri

@@ -53,6 +53,8 @@ SOURCES += \
 
 win32:!winrt: SOURCES += image/qpixmap_win.cpp
 
+darwin: OBJECTIVE_SOURCES += image/qimage_darwin.mm
+
 NO_PCH_SOURCES += image/qimage_compat.cpp
 false: SOURCES += $$NO_PCH_SOURCES # Hack for QtCreator
 

src/gui/image/qimage.h

@@ -54,6 +54,10 @@
 #include <QtCore/qstringlist.h>
 #endif
 
+#if defined(Q_OS_DARWIN) || defined(Q_QDOC)
+Q_FORWARD_DECLARE_MUTABLE_CG_TYPE(CGImage);
+#endif
+
 QT_BEGIN_NAMESPACE
 
 
@@ -321,6 +325,11 @@ public:
     static QPixelFormat toPixelFormat(QImage::Format format) Q_DECL_NOTHROW;
     static QImage::Format toImageFormat(QPixelFormat format) Q_DECL_NOTHROW;
 
+    // Platform spesific conversion functions
+#if defined(Q_OS_DARWIN) || defined(Q_QDOC)
+    CGImageRef toCGImage() const Q_DECL_CF_RETURNS_RETAINED;
+#endif
+
 #if QT_DEPRECATED_SINCE(5, 0)
     QT_DEPRECATED inline QString text(const char *key, const char *lang = Q_NULLPTR) const;
     QT_DEPRECATED inline QList<QImageTextKeyLang> textList() const;

src/gui/image/qimage_darwin.mm

@@ -0,0 +1,141 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 The Qt Company Ltd.
+** Contact: http://www.qt.io/licensing/
+**
+** This file is part of the QtGui module of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 http://www.qt.io/terms-conditions. For further
+** information use the contact form at http://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 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** As a special exception, The Qt Company gives you certain additional
+** rights. These rights are described in The Qt Company LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#include "qimage.h"
+
+#include <private/qcore_mac_p.h>
+
+#import <Foundation/Foundation.h>
+#import <CoreGraphics/CoreGraphics.h>
+
+QT_BEGIN_NAMESPACE
+
+/*!
+    Creates a \c CGImage equivalent to the QImage \a image. Returns a
+    \c CGImageRef handle.
+
+    The returned CGImageRef partakes in the QImage implicit sharing,
+    and holds a reference to the QImage data. CGImage is immutable
+    and will never detach the QImage. Writing to the QImage will detach
+    as usual.
+
+    This function is fast, and does not copy or convert image data.
+
+    The following image formats are supported, and will be mapped to
+    a corresponding native image type:
+
+    \table
+    \header
+        \li Qt
+        \li CoreGraphics
+    \row
+        \li Format_ARGB32
+        \li kCGImageAlphaFirst | kCGBitmapByteOrder32Host
+    \row
+        \li Format_RGB32
+        \li kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host
+    \row
+        \li Format_RGBA8888_Premultiplied
+        \li kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big
+    \row
+        \li Format_RGBA8888
+        \li kCGImageAlphaLast | kCGBitmapByteOrder32Big
+    \row
+        \li Format_RGBX8888
+        \li kCGImageAlphaNoneSkipLast | kCGBitmapByteOrder32Big
+    \row
+        \li Format_ARGB32_Premultiplied
+        \li kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host
+    \endtable
+
+    Other formats are not supported; this function returns a null
+    CGImageRef for those cases. Users of this function may then
+    convert the QImage to a supported formate first, for example
+    Format_ARGB32_Premultiplied.
+
+    The CGImageRef color space is set to the sRGB color space.
+
+    \sa toNSImage()
+*/
+CGImageRef QImage::toCGImage() const
+{
+    if (isNull())
+        return nil;
+
+    // Determine the target native format
+    uint cgflags = kCGImageAlphaNone;
+    switch (format()) {
+    case QImage::Format_ARGB32:
+        cgflags = kCGImageAlphaFirst | kCGBitmapByteOrder32Host;
+        break;
+    case QImage::Format_RGB32:
+        cgflags = kCGImageAlphaNoneSkipFirst | kCGBitmapByteOrder32Host;
+        break;
+    case QImage::Format_RGBA8888_Premultiplied:
+        cgflags = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;
+        break;
+    case QImage::Format_RGBA8888:
+        cgflags = kCGImageAlphaLast | kCGBitmapByteOrder32Big;
+        break;
+    case QImage::Format_RGBX8888:
+        cgflags = kCGImageAlphaNoneSkipLast | kCGBitmapByteOrder32Big;
+        break;
+    case QImage::Format_ARGB32_Premultiplied:
+        cgflags = kCGImageAlphaPremultipliedFirst | kCGBitmapByteOrder32Host;
+        break;
+    default: break;
+    }
+
+    // Format not supported: return nil CGImageRef
+    if (cgflags == kCGImageAlphaNone)
+        return nil;
+
+    // Create a data provider that owns a copy of the QImage and references the image data.
+    auto deleter = [](void *image, const void *, size_t)
+                   { delete static_cast<QImage *>(image); };
+    QCFType<CGDataProviderRef> dataProvider =
+        CGDataProviderCreateWithData(new QImage(*this), bits(), byteCount(), deleter);
+
+    QCFType<CGColorSpaceRef> colorSpace =  CGColorSpaceCreateWithName(kCGColorSpaceSRGB);
+
+    const size_t bitsPerComponent = 8;
+    const size_t bitsPerPixel = 32;
+    const CGFloat *decode = nullptr;
+    const bool shouldInterpolate = false;
+
+    return CGImageCreate(width(), height(), bitsPerComponent, bitsPerPixel,
+                         this->bytesPerLine(), colorSpace, cgflags, dataProvider,
+                         decode, shouldInterpolate, kCGRenderingIntentDefault);
+}
+
+QT_END_NAMESPACE

tests/auto/gui/image/qimage/tst_qimage.cpp

@@ -39,6 +39,10 @@
 #include <private/qimage_p.h>
 #include <private/qdrawhelper_p.h>
 
+#ifdef Q_OS_DARWIN
+#include <CoreGraphics/CoreGraphics.h>
+#endif
+
 Q_DECLARE_METATYPE(QImage::Format)
 Q_DECLARE_METATYPE(Qt::GlobalColor)
 
@@ -201,6 +205,11 @@ private slots:
     void ditherGradient_data();
     void ditherGradient();
 
+#ifdef Q_OS_DARWIN
+    void toCGImage_data();
+    void toCGImage();
+#endif
+
 private:
     const QString m_prefix;
 };
@@ -3307,5 +3316,41 @@ void tst_QImage::ditherGradient()
     QVERIFY(observedGradientSteps >= minimumExpectedGradient);
 }
 
+#ifdef Q_OS_DARWIN
+
+void tst_QImage::toCGImage_data()
+{
+    QTest::addColumn<QImage::Format>("format");
+    QTest::addColumn<bool>("supported");
+
+    // Populate test data with supported status for all QImage formats.
+    QSet<QImage::Format> supported =
+        { QImage::Format_ARGB32, QImage::Format_RGB32, QImage::Format_RGBA8888_Premultiplied,
+          QImage::Format_RGBA8888, QImage::Format_RGBX8888, QImage::Format_ARGB32_Premultiplied };
+
+    for (int i = QImage::Format_Invalid; i < QImage::Format_Grayscale8; ++i) {
+        QTest::newRow(qPrintable(formatToString(QImage::Format(i))))
+            << QImage::Format(i) << supported.contains(QImage::Format(i));
+    }
+}
+
+// Verify that toCGImage() returns a valid CGImageRef for supported image formats.
+void tst_QImage::toCGImage()
+{
+    QFETCH(QImage::Format, format);
+    QFETCH(bool, supported);
+
+    QImage qimage(64, 64, format);
+    qimage.fill(Qt::red);
+
+    CGImageRef cgimage = qimage.toCGImage();
+    QCOMPARE(cgimage != nullptr, supported);
+
+    CGImageRelease(cgimage);
+}
+
+#endif
+
+
 QTEST_GUILESS_MAIN(tst_QImage)
 #include "tst_qimage.moc"