实现绘图功能 通过UISegmentedControl来选择不同颜色的画笔-Brush drawing functions UISegmentedControl to choose different colors

paint code, colors, gradients and shadows can form relationships. A new color can be derived from an existing one simply by using the built-in operations. Gradients and shadows can also be derived from colors in the library.

Objective-C实现的涂鸦板，可以选择不同颜色和不同粗细的画笔，支持清屏，回退和保存图片-Doodle board Objective-C to achieve, can choose different colors and different thickness of the brush, support screen, back off and save pictures