【转】代码让UIImage具有渐变效果

转自：http://blog.sina.com.cn/s/blog_7ccde1bf0100v9ni.html

做一个UIImage的category，直接上代码：

1 - (UIImage *) imageWithBackgroundColor:(UIColor *)bgColor
2                            shadeAlpha1:(CGFloat)alpha1
3                            shadeAlpha2:(CGFloat)alpha2
4                            shadeAlpha3:(CGFloat)alpha3
5                            shadowColor:(UIColor *)shadowColor
6                           shadowOffset:(CGSize)shadowOffset
7                             shadowBlur:(CGFloat)shadowBlur {
8     UIImage *image = self;
9     CGColorRef cgColor = [bgColor CGColor];
10     CGColorRef cgShadowColor = [shadowColor CGColor];
11     CGFloat components[16] = {1,1,1,alpha1,1,1,1,alpha1,1,1,1,alpha2,1,1,1,alpha3};
12     CGFloat locations[4] = {0,0.5,0.6,1};
13     CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
14     CGGradientRef colorGradient = CGGradientCreateWithColorComponents(colorSpace, components, locations, (size_t)4);
15     CGRect contextRect;
16     contextRect.origin.x = 0.0f;
17     contextRect.origin.y = 0.0f;
18     contextRect.size = [image size];
19     //contextRect.size = CGSizeMake([image size].width+5,[image size].height+5);
20     // Retrieve source image and begin image context
21     UIImage *itemImage = image;
22     CGSize itemImageSize = [itemImage size];
23     CGPoint itemImagePosition;
24     itemImagePosition.x = ceilf((contextRect.size.width - itemImageSize.width) / 2);
25     itemImagePosition.y = ceilf((contextRect.size.height - itemImageSize.height) / 2);
26     UIGraphicsBeginImageContext(contextRect.size);
27     CGContextRef c = UIGraphicsGetCurrentContext();
28     // Setup shadow
29     CGContextSetShadowWithColor(c, shadowOffset, shadowBlur, cgShadowColor);
30     // Setup transparency layer and clip to mask
31     CGContextBeginTransparencyLayer(c, NULL);
32     CGContextScaleCTM(c, 1.0, -1.0);
33     CGContextClipToMask(c, CGRectMake(itemImagePosition.x, -itemImagePosition.y, itemImageSize.width, -itemImageSize.height), [itemImage CGImage]);
34     // Fill and end the transparency layer
35     CGContextSetFillColorWithColor(c, cgColor);
36     contextRect.size.height = -contextRect.size.height;
37     CGContextFillRect(c, contextRect);
38     CGContextDrawLinearGradient(c, colorGradient,CGPointZero,CGPointMake(contextRect.size.width*1.0/4.0,contextRect.size.height),0);
39     CGContextEndTransparencyLayer(c);
40     //CGPointMake(contextRect.size.width*3.0/4.0, 0)
41     // Set selected image and end context
42     UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
43     UIGraphicsEndImageContext();
44     CGColorSpaceRelease(colorSpace);
45     CGGradientRelease(colorGradient);
46     return resultImage;
47 }

用法如下

1 UIImage *niceImage = [[UIImage imageNamed:@"image_name"] imageWithBackgroundColor:[UIColor colorWithRed:41.0/255.0 green:147.0/255.0 blue:239.0/255.0 alpha:1.0]
2                                                                       shadeAlpha1:0.6
3                                                                       shadeAlpha2:0.0
4                                                                       shadeAlpha3:0.4
5                                                                       shadowColor:[UIColor blackColor]
6                                                                      shadowOffset:CGSizeMake(0.0f, -1.0f)
7                                                                        shadowBlur:3.0];

posted on 2012-05-23 11:50 该显示名称已被其他用户使用阅读(409) 评论(0) 收藏举报