渐变颜色到CGContextRef

我正在使用CGContextRef绘制4弧。我可以填充颜色，但现在我想设置渐变颜色的弧。我做了它。它工作正常。现在我想为每个弧设置不同的颜色。是否有任何方法可以做它？请帮助我。我附上我的代码和截图的弧。代码：

CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB(); CGFloat comps[] = {1.0,1.0,1.0,1.0,0.0,1.0,1.0,1.0}; CGFloat locs[] = {0,1}; CGGradientRef g = CGGradientCreateWithColorComponents(space, comps, locs, 2); CGContextRef context = UIGraphicsGetCurrentContext(); CGFloat startAngle = 0; CGFloat endAngle = 90; CGFloat radius = 100.0; CGFloat levelWidth = 50; for (int i = 0; i < 4; i++) { CGContextMoveToPoint(context, self.bounds.size.width/2, self.bounds.size.height/2); CGContextAddArc(context, self.bounds.size.width/2, self.bounds.size.height/2, radius, DEGREES_RADIANS(startAngle), DEGREES_RADIANS(endAngle), NO); CGContextAddArc(context, self.bounds.size.width/2, self.bounds.size.height/2, radius - levelWidth, DEGREES_RADIANS(endAngle),DEGREES_RADIANS(startAngle), YES); startAngle = endAngle; endAngle = endAngle + 90; CGContextClosePath(context); } //CGContextClosePath(context); CGContextClip(context); CGContextDrawRadialGradient(context, g, CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2), 1.0f, CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2), 150, 0); 

和屏幕截图：

Answer 1

在剪切，剪切和绘制圆弧之前，您希望使用CGContextSaveGState保存上下文，然后在绘制下一个圆弧之前使用CGContextRestoreGState恢复上下文。 你显然想要一个CGGradientRef数组。 从而：

 CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB(); CGGradientRef g[4]; CGFloat comps0[] = {1.0,1.0,1.0,1.0,0.0,1.0,1.0,1.0}; CGFloat locs[] = {0,1}; g[0] = CGGradientCreateWithColorComponents(space, comps0, locs, 2); CGFloat comps1[] = {1.0,1.0,1.0,1.0,1.0,0.0,1.0,1.0}; g[1] = CGGradientCreateWithColorComponents(space, comps1, locs, 2); CGFloat comps2[] = {1.0,1.0,1.0,1.0,1.0,1.0,0.0,1.0}; g[2] = CGGradientCreateWithColorComponents(space, comps2, locs, 2); CGFloat comps3[] = {1.0,1.0,1.0,1.0,0.5,0.0,0.5,1.0}; g[3] = CGGradientCreateWithColorComponents(space, comps3, locs, 2); CGContextRef context = UIGraphicsGetCurrentContext(); CGFloat startAngle = 0; CGFloat endAngle = 90; CGFloat radius = 100.0; CGFloat levelWidth = 50; for (int i = 0; i < 4; i++) { CGContextSaveGState(context); CGContextMoveToPoint(context, self.bounds.size.width/2, self.bounds.size.height/2); CGContextAddArc(context, self.bounds.size.width/2, self.bounds.size.height/2, radius, DEGREES_RADIANS(startAngle), DEGREES_RADIANS(endAngle), NO); CGContextAddArc(context, self.bounds.size.width/2, self.bounds.size.height/2, radius - levelWidth, DEGREES_RADIANS(endAngle),DEGREES_RADIANS(startAngle), YES); startAngle = endAngle; endAngle = endAngle + 90; CGContextClosePath(context); CGContextClip(context); CGContextDrawRadialGradient(context, g[i], CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2), 1.0f, CGPointMake(self.bounds.size.width/2, self.bounds.size.height/2), 150, 0); CGContextRestoreGState(context); CGGradientRelease(g[i]); // don't forget to release the gradient }