圆筒绘画

CGContextRef context=UIGraphicsGetCurrentContext();
    CGColorSpaceRef colorSp=CGColorSpaceCreateDeviceRGB();
    CGFloat components[]={1.0,0.0,0.0,1.0,
                        0,1,0,1,
                        0,0,1,1
                       };
    CGFloat location[]={0.1,0.5,0.9};
    CGGradientRef gradient=CGGradientCreateWithColorComponents(colorSp, components, location, 3);
    //创建一直线，沿直线渐变
//    CGContextDrawLinearGradient(context, gradient, CGPointMake(0, 50), CGPointMake(50, 150), 0);

    CGContextDrawRadialGradient(context, gradient, CGPointMake(200, 300), 130, CGPointMake(100, 200), 60, 0);

//    CGContextStrokePath(context);

    //圆筒
    int j=10;
    for (int i=60; i<270; i=i+10) {
        j=j+5;
        CGContextDrawRadialGradient(context, gradient, CGPointMake(150, i),j, CGPointMake(150, i+10),j+4, 0);
    }