Image Brightness Contrast Curve Adjust Qt impl demo
Base on qt just like photoshop
Features：
1、Multi points curve control
2、Histogram show
3、Gray image curve adjust
4、Color image curve adjust with 3 mode
（1）all channel total adjust
（2）single channel adjust
（3）Multi channel adjust
Demo manual： 1、top menu “Adjust” -》“Open” to open an image file
2、top menu “Adjust” -》“Curve Adjust” to adjust image
spline lib is from ： https://people.sc.fsu.edu/~jburkardt/c_src/spline/spline.html
and i modify some method return type(origin is exit(-1) change to return nullptr)
aaCurve impl is from： https://github.com/pyzhangxiang/qt-curve-editor
and i add function: aaCurvePtr createCurve(const std::vector<std::pair<unsigned char, unsigned char> >& spline_data, SplineType type) use to load data from std vector