WPF实现的圆形进度条，类似安卓手机上的圆形进度条效果。-WPF achieve circular progress bar, similar to the effect of the circular progress bar on the Android phone.

wpf圆形进度条,根据进度自动变色,开始颜色为红色,结束颜色为绿色(WPF circular progress bar, according to progress automatically change color, start color is red, end color is green)