怎樣繪製徑向漸變（iphone）一個部門

Question

怎樣繪製在客觀C（核芯顯卡） 徑向漸變一個部門（填弧）我用

CGContextDrawRadialGradient 

，但它提請圈。 如果你說我如何用徑向漸變填充任何形狀，這將是一件好事。謝謝

Answer 1

添加當前上下文的路徑，該路徑定義所需的形狀並在繪製之前剪切上下文。示例代碼：

- (void)drawRect:(CGRect)rect 
{ 
    CGPoint c = self.center ; 
    // Drawing code 
    CGContextRef cx = UIGraphicsGetCurrentContext(); 

    CGContextSaveGState(cx); 
    CGColorSpaceRef space = CGColorSpaceCreateDeviceRGB(); 

    CGFloat comps[] = {1.0,1.0,0.0,1.0,0.0,1.0,0.0,1.0}; 
    CGFloat locs[] = {0,1}; 
    CGGradientRef g = CGGradientCreateWithColorComponents(space, comps, locs, 2); 


    CGMutablePathRef path = CGPathCreateMutable(); 
    CGPathMoveToPoint(path, NULL, c.x, c.y); 
    CGPathAddLineToPoint(path, NULL, c.x, c.y-100); 
    CGPathAddArcToPoint(path, NULL, c.x+100, c.y-100, c.x+100, c.y, 100); 
    CGPathAddLineToPoint(path, NULL, c.x, c.y); 

    CGContextAddPath(cx, path); 
    CGContextClip(cx); 

    CGContextDrawRadialGradient(cx, g, c, 1.0f, c, 320.0f, 0); 

    CGContextRestoreGState(cx); 
    ... // Do some more drawing may be 
}