渐变效果图.pic.jpg

使用：
    //107, 140, 174  --- 37, 70, 102
    //设置view 背景渐变颜色
    UIImage *backImage = [UIImage gradientImageWithBounds:RECT(0, 0, WindowWidth, WindowHeight) andColors:@[RGBCOLOR(107, 140, 174), RGBCOLOR(37, 70, 102)] andGradientType:GradientDirectionTopToBottom];
    UIColor *bgColor = [UIColor colorWithPatternImage:backImage];
    [self.view setBackgroundColor:bgColor];

CGGradientRef 绘制效果和速度都是比较coreImage好的。

typedef NS_ENUM(NSInteger, GradientDirection) {
    GradientDirectionTopToBottom = 0,    // 从上往下 渐变
    GradientDirectionLeftToRight,        // 从左往右
    GradientDirectionBottomToTop,      // 从下往上
    GradientDirectionRightToLeft      // 从右往左
};

/**
 *  @brief  生成渐变色图片
 *
 *  @param  bounds  图片的大小
 *  @param  colors      渐变颜色组
 *  @param  gradientType     渐变方向
 *
 *  @return 图片
 */
+ (UIImage*)gradientImageWithBounds:(CGRect)bounds andColors:(NSArray*)colors andGradientType:(GradientDirection)gradientType{
    NSMutableArray *ar = [NSMutableArray array];
    
    for(UIColor *c in colors) {
        [ar addObject:(id)c.CGColor];
    }
    UIGraphicsBeginImageContextWithOptions(bounds.size, YES, 1);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSaveGState(context);
    CGColorSpaceRef colorSpace = CGColorGetColorSpace([[colors lastObject] CGColor]);
    CGGradientRef gradient = CGGradientCreateWithColors(colorSpace, (CFArrayRef)ar, NULL);
    CGPoint startPt =  CGPointMake(0.0, 0.0);
    CGPoint endPt =  CGPointMake(0.0, 0.0);
    
    switch (gradientType) {
        case GradientDirectionTopToBottom:
            startPt= CGPointMake(0.0, 0.0);
            endPt= CGPointMake(0.0, bounds.size.height);
            break;
        case GradientDirectionLeftToRight:
            startPt = CGPointMake(0.0, 0.0);
            endPt = CGPointMake(bounds.size.width, 0.0);
            break;
        case GradientDirectionBottomToTop:
            startPt = CGPointMake(0.0, bounds.size.height);
            endPt = CGPointMake(0.0, 0.0);
            break;
        case GradientDirectionRightToLeft:
            startPt = CGPointMake(bounds.size.width, 0.0);
            endPt = CGPointMake(0, 0.0);
            break;
    }
    CGContextDrawLinearGradient(context, gradient, startPt, endPt, kCGGradientDrawsBeforeStartLocation | kCGGradientDrawsAfterEndLocation);
    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    CGGradientRelease(gradient);
    CGContextRestoreGState(context);
    CGColorSpaceRelease(colorSpace);
    UIGraphicsEndImageContext();
    return image;
}