drawGradientImageFromColor

drawGradientImageFromColor.m

#import <Foundation/Foundation.h>

...

- (UIImage *)drawGradientImageFromColor:(UIColor *)beginColor toColor:(UIColor *)endColor imageSize:(CGSize)imageSize
{
    //   set sideline width
    CGFloat lineWidth = 3.0f;
    //   set a canvas, and use the imageSize
    UIGraphicsBeginImageContextWithOptions(imageSize, NO, 0);
    //   set RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    //   set draw context
    CGContextRef context = UIGraphicsGetCurrentContext();
    //   set color to array
    NSArray *gradientColors = [NSArray arrayWithObjects:(id) beginColor.CGColor, (id) endColor.CGColor, nil];
    //   set range 0~1
    //   two value, cause two color
    //   if more color, add more value
    CGFloat gradientLocation[] = { 0, 1 };
    //   set gradient info
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (__bridge CFArrayRef)gradientColors, gradientLocation);
    //   set rectangle path for bezier path
    UIBezierPath * bezierPath = [UIBezierPath bezierPathWithRect:CGRectMake(0, 0, imageSize.width, imageSize.height)];
    CGContextSaveGState(context);
    [bezierPath addClip];
    //   set gradient start point and end point
    CGPoint beginPoint = CGPointMake(imageSize.width / 2, 0);
    CGPoint endPoint = CGPointMake(imageSize.width / 2, imageSize.height);
    //   add position to linear gradient
    CGContextDrawLinearGradient(context, gradient, beginPoint, endPoint, 0);
    //   set sideline info
    CGContextSetStrokeColorWithColor(context, [[UIColor blackColor] CGColor]);
    //   draw sideline
    [bezierPath setLineWidth:lineWidth];
    //   fill gradient color
    [bezierPath stroke];
    CGContextRestoreGState(context);
    //   output context to image
    UIImage * image = UIGraphicsGetImageFromCurrentImageContext();
    //   context end and release
    UIGraphicsEndImageContext();
    CGColorSpaceRelease(colorSpace);
    CGGradientRelease(gradient);
    return image;
}

http://carlos-blog.logdown.com/posts/2013/09/14/ios-uiimage-with-gradient-color