CGContextAddArc中的渐变？

Question

我在DrawRect中使用以下代码绘制圆弧......我想只用渐变效果绘制圆弧......请帮忙吗？

              CGContextSetAlpha(ctx, 0.5);
            CGContextSetRGBFillColor(ctx, color.red, color.green, color.blue, color.alpha );
            CGContextMoveToPoint(ctx, cX, cY);
            CGContextAddArc(ctx, cX, cY, radious+10, (startDeg-90)*M_PI/180.0, (endDeg-90)*M_PI/180.0, 0);
            CGContextClosePath(ctx);
            CGContextFillPath(ctx);

Answer 1

首先创建一个弧然后使用以下代码将渐变效果应用于路径

CGGradientRef glossGradient;
CGColorSpaceRef rgbColorspace;
size_t num_locations = 2;
CGFloat locations[2] = { 0.0, 1.0 };
CGFloat components[8] = { 0.965, 0.965, 0.965, 1.0, // Start color
    0.603, 0.603, 0.603, 1.0 }; // End color

rgbColorspace = CGColorSpaceCreateDeviceRGB();
glossGradient = CGGradientCreateWithColorComponents(rgbColorspace, components, locations, num_locations);

CGRect currentBounds = self.bounds;
CGPoint topCenter = CGPointMake(CGRectGetMidX(currentBounds), 0.0f);
CGPoint midCenter = CGPointMake(CGRectGetMidX(currentBounds), CGRectGetMaxY(currentBounds));
CGContextDrawLinearGradient(UIGraphicsGetCurrentContext(), glossGradient, topCenter, midCenter, 0);

CGGradientRelease(glossGradient);
CGColorSpaceRelease(rgbColorspace);