CGGradientRef

gistfile1.txt

- (void)drawGradientWithContext:(CGContextRef)context colors:(NSArray <id> *)colors path:(CGPathRef)path
                            aplha:(CGFloat)alpha startPointY:(CGFloat)startY {
    
    
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGFloat locations[] = {0.0, 1.0};
    CGContextSaveGState(context);
    
    CGContextAddPath(context, path);
    CGContextClip(context);
    CGContextSetAlpha(context, alpha);
    
    CGRect pathRect = CGPathGetBoundingBox(path);
    
    CGPoint startPoint = CGPointMake(CGRectGetMidX(pathRect), CGRectGetMinY(pathRect));
    CGPoint endPoint = CGPointMake(CGRectGetMidX(pathRect), CGRectGetMaxY(pathRect));
    
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)colors, locations);
    CGContextDrawLinearGradient(context, gradient, startPoint, endPoint, kCGGradientDrawsBeforeStartLocation);
    
    CGContextRestoreGState(context);
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
}