How to perform HSV Color mixing ?

Hi Experts,
i have extracted RGB values of image and converted it to Qcolor, and the QColor with RGB converted to HSV
like below,
QColor colorRGB = QColor(line[ x ]);
QColor colorHSV = colorRGB.toHsv();

Now i can extract colorHSV.hue(),colorHSV .saturation(),colorHSV .value() seperately, Could anyone suggest how to perform
mixing of HSV contrast,brightness etc..

Thanks
AshKetchup

This is not Qt issue - but color theory - wrong forum.