关于图形的学习笔记1

1.颜色的反向提取，获得各个颜色的分量和透明度；

 UIColor *oringeColor =[UIColorcolorWithRed:0.3fgreen:0.4fblue:0.7falpha:0.9f];

   CGColorRef colorRef = oringeColor.CGColor;

   const CGFloat *components =CGColorGetComponents(colorRef);

   NSUIntegercomponentsCount = CGColorGetNumberOfComponents(colorRef);

   NSUInteger counter = 0  ;

   for (counter = 0; counter < componentsCount; counter++) {

       NSLog(@"Component %lu = %.02f",(unsignedlong)counter + 1 , components[counter]);

    }

打印出来的值为：

2017-04-11 15:06:07.722 text[35612:4178132] Component 1 = 0.30

2017-04-11 15:06:07.723 text[35612:4178132] Component 2 = 0.40

2017-04-11 15:06:07.723 text[35612:4178132] Component 3 = 0.70

2017-04-11 15:06:07.723 text[35612:4178132] Component 4 = 0.90