Improve CMYK writing support

Closes #11 

Requires MR !279

On formats that does not support CMYK and does not use the ScanLineConverter class during write operation, the CMYK images must be converted using the color space conversion functions of `QImage` (if ICC profile is valid).

src/imageformats/avif.cpp

@@ -686,7 +686,18 @@ bool QAVIFHandler::write(const QImage &image)
             }
         }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+        QImage tmpcolorimage;
+        auto cs = image.colorSpace();
+        if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+            tmpcolorimage = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), tmpformat);
+        }
+        else {
+            tmpcolorimage = image.convertToFormat(tmpformat);
+        }
+#else
         QImage tmpcolorimage = image.convertToFormat(tmpformat);
+#endif
 
         avifPixelFormat pixel_format = AVIF_PIXEL_FORMAT_YUV420;
         if (m_quality >= KIMG_AVIF_QUALITY_HIGH) {

src/imageformats/heif.cpp

@@ -159,7 +159,18 @@ bool HEIFHandler::write_helper(const QImage &image)
         }
     }
 
-    const QImage tmpimage = image.convertToFormat(tmpformat);
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    QImage tmpimage;
+    auto cs = image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+        tmpimage = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), tmpformat);
+    }
+    else {
+        tmpimage = image.convertToFormat(tmpformat);
+    }
+#else
+    QImage tmpimage = image.convertToFormat(tmpformat);
+#endif
 
     struct heif_context *context = heif_context_alloc();
     struct heif_error err;

src/imageformats/jxl.cpp

@@ -584,6 +584,9 @@ bool QJpegXLHandler::write(const QImage &image)
     case QImage::Format_RGBX8888:
     case QImage::Format_RGBA8888:
     case QImage::Format_RGBA8888_Premultiplied:
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    case QImage::Format_CMYK8888:
+#endif
         save_depth = 8;
         break;
     case QImage::Format_Grayscale16:
@@ -757,7 +760,20 @@ bool QJpegXLHandler::write(const QImage &image)
         }
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    // TODO: add native CMYK support (libjxl supports CMYK images)
+    QImage tmpimage;
+    auto cs = image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+        tmpimage = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), tmpformat);
+    }
+    else {
+        tmpimage = image.convertToFormat(tmpformat);
+    }
+#else
     QImage tmpimage = image.convertToFormat(tmpformat);
+#endif
+
     const size_t xsize = tmpimage.width();
     const size_t ysize = tmpimage.height();
 

src/imageformats/pcx.cpp

@@ -9,6 +9,7 @@
 #include "util_p.h"
 
 #include <QColor>
+#include <QColorSpace>
 #include <QDataStream>
 #include <QDebug>
 #include <QImage>
@@ -877,6 +878,12 @@ bool PCXHandler::write(const QImage &image)
     s.setByteOrder(QDataStream::LittleEndian);
 
     QImage img = image;
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    auto cs = image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+        img = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb));
+    }
+#endif
 
     const int w = img.width();
     const int h = img.height();

src/imageformats/pic.cpp

@@ -17,10 +17,12 @@
 #include "rle_p.h"
 #include "util_p.h"
 
+#include <QColorSpace>
 #include <QDataStream>
 #include <QDebug>
 #include <QImage>
 #include <QVariant>
+
 #include <algorithm>
 #include <functional>
 #include <qendian.h>
@@ -264,7 +266,16 @@ bool SoftimagePICHandler::read(QImage *image)
 bool SoftimagePICHandler::write(const QImage &_image)
 {
     bool alpha = _image.hasAlphaChannel();
-    const QImage image = _image.convertToFormat(alpha ? QImage::Format_ARGB32 : QImage::Format_RGB32);
+    QImage image;
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    auto cs = _image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && _image.format() == QImage::Format_CMYK8888) {
+        image = _image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), QImage::Format_RGB32);
+    }
+#endif
+    if (image.isNull()) {
+        image = _image.convertToFormat(alpha ? QImage::Format_ARGB32 : QImage::Format_RGB32);
+    }
 
     if (image.width() < 0 || image.height() < 0) {
         qDebug() << "Image size invalid:" << image.width() << image.height();
@@ -289,7 +300,7 @@ bool SoftimagePICHandler::write(const QImage &_image)
     stream << channels;
 
     for (int r = 0; r < image.height(); r++) {
-        const QRgb *row = reinterpret_cast<const QRgb *>(image.scanLine(r));
+        const QRgb *row = reinterpret_cast<const QRgb *>(image.constScanLine(r));
 
         /* Write the RGB part of the scanline */
         auto rgbEqual = [](QRgb p1, QRgb p2) -> bool {

src/imageformats/rgb.cpp

@@ -24,11 +24,11 @@
 
 #include <cstring>
 
-#include <QList>
-#include <QMap>
-
+#include <QColorSpace>
 #include <QDebug>
 #include <QImage>
+#include <QList>
+#include <QMap>
 
 class RLEData : public QList<uchar>
 {
@@ -750,7 +750,14 @@ bool SGIImagePrivate::writeImage(const QImage &image)
         _dim = 3, _zsize++;
     }
 
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    auto cs = image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+        img = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), QImage::Format_RGB32);
+    } else if (hasAlpha && img.format() != QImage::Format_ARGB32) {
+#else
     if (hasAlpha && img.format() != QImage::Format_ARGB32) {
+#endif
         img = img.convertToFormat(QImage::Format_ARGB32);
     } else if (!hasAlpha && img.format() != QImage::Format_RGB32) {
         img = img.convertToFormat(QImage::Format_RGB32);

src/imageformats/tga.cpp

@@ -21,6 +21,7 @@
 
 #include <assert.h>
 
+#include <QColorSpace>
 #include <QDataStream>
 #include <QDebug>
 #include <QImage>
@@ -474,7 +475,14 @@ bool TGAHandler::write(const QImage &image)
 
     QImage img(image);
     const bool hasAlpha = img.hasAlphaChannel();
+#if QT_VERSION >= QT_VERSION_CHECK(6, 8, 0)
+    auto cs = image.colorSpace();
+    if (cs.isValid() && cs.colorModel() == QColorSpace::ColorModel::Cmyk && image.format() == QImage::Format_CMYK8888) {
+        img = image.convertedToColorSpace(QColorSpace(QColorSpace::SRgb), QImage::Format_RGB32);
+    } else if (hasAlpha && img.format() != QImage::Format_ARGB32) {
+#else
     if (hasAlpha && img.format() != QImage::Format_ARGB32) {
+#endif
         img = img.convertToFormat(QImage::Format_ARGB32);
     } else if (!hasAlpha && img.format() != QImage::Format_RGB32) {
         img = img.convertToFormat(QImage::Format_RGB32);
@@ -497,7 +505,7 @@ bool TGAHandler::write(const QImage &image)
     s << quint8(hasAlpha ? originTopLeft + alphaChannel8Bits : originTopLeft);   // top left image (0x20) + 8 bit alpha (0x8)
 
     for (int y = 0; y < img.height(); y++) {
-        auto ptr = reinterpret_cast<QRgb *>(img.scanLine(y));
+        auto ptr = reinterpret_cast<const QRgb *>(img.constScanLine(y));
         for (int x = 0; x < img.width(); x++) {
             auto color = *(ptr + x);
             s << quint8(qBlue(color));