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 }
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];
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];