exr: write support and more

- Added support for writing EXR files
- Large image support (tested with 32GiB 16-bit image)
- OpenEXR multithreaded read/write support through the use of line blocks
- Build option to enable conversion to sRGB when read (disabled by default)
- Multi-view image reading support
- Options support: Size, ImageFormat, Quality, CompressRatio
- Metadata write/read support via EXR attributes

The plugin is now quite complete. It should also work on KF5 (not tested): if there is the will to include this MR also on KF5, let me know and I will do all the necessary tests.

src/imageformats/scanlineconverter_p.h

@@ -42,6 +42,14 @@ public:
     void setTargetColorSpace(const QColorSpace &colorSpace);
     QColorSpace targetColorSpace() const;
 
+    /*!
+     * \brief setDefaultSourceColorSpace
+     * Set the source color space to use when the image does not have a color space.
+     * \param colorSpace
+     */
+    void setDefaultSourceColorSpace(const QColorSpace &colorSpace);
+    QColorSpace defaultSourceColorSpace() const;
+
     /*!
      * \brief convertedScanLine
      * Convert the scanline \a y.
@@ -62,14 +70,24 @@ public:
      * \note Only 24 bit or grater images.
      * \param image The source image.
      * \param targetColorSpace The target color space.
+     * \param defaultColorSpace The default color space to use it image does not contains one.
      * \return True if the conversion should be done otherwise false.
      */
-    bool isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace) const;
+    static bool isColorSpaceConversionNeeded(const QImage &image, const QColorSpace &targetColorSpace, const QColorSpace &defaultColorSpace = QColorSpace());
+
+    /*!
+     * \brief isColorSpaceConversionNeeded
+     */
+    inline bool isColorSpaceConversionNeeded(const QImage &image) const
+    {
+        return isColorSpaceConversionNeeded(image, _colorSpace, _defaultColorSpace);
+    }
 
 private:
     // data
     QImage::Format _targetFormat;
     QColorSpace _colorSpace;
+    QColorSpace _defaultColorSpace;
 
     // internal buffers
     QImage _tmpBuffer;