【转】UIImage的灰化处理

转自：http://blog.sina.com.cn/s/blog_7ccde1bf0100v9oj.html

1 - (UIImage *) convertToGreyscale:(UIImage *)i {
2     int kRed = 1;
3     int kGreen = 2;
4     int kBlue = 4;
5     int colors = kGreen;
6     int m_width = i.size.width;
7     int m_height = i.size.height;
8     uint32_t *rgbImage = (uint32_t *) malloc(m_width * m_height * sizeof(uint32_t));
9     CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
10     CGContextRef context = CGBitmapContextCreate(rgbImage, m_width, m_height, 8, m_width * 4, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
11     CGContextSetInterpolationQuality(context, kCGInterpolationHigh);
12     CGContextSetShouldAntialias(context, NO);
13     CGContextDrawImage(context, CGRectMake(0, 0, m_width, m_height), [i CGImage]);
14     CGContextRelease(context);
15     CGColorSpaceRelease(colorSpace);
16     // now convert to grayscale
17     uint8_t *m_imageData = (uint8_t *) malloc(m_width * m_height);
18     for(int y = 0; y < m_height; y++) {
19         for(int x = 0; x < m_width; x++) {
20                 uint32_t rgbPixel=rgbImage[y*m_width+x];
21                 uint32_t sum=0,count=0;
22                 if (colors & kRed) {sum += (rgbPixel>>24)&255; count++;}
23                 if (colors & kGreen) {sum += (rgbPixel>>16)&255; count++;}
24                 if (colors & kBlue) {sum += (rgbPixel>>8)&255; count++;}
25                 m_imageData[y*m_width+x]=sum/count;
26         }
27     }
28     free(rgbImage);
29     // convert from a gray scale image back into a UIImage
30     uint8_t *result = (uint8_t *) calloc(m_width * m_height *sizeof(uint32_t), 1);
31     // process the image back to rgb
32     for(int i = 0; i < m_height * m_width; i++) {
33         result[i*4]=0;
34         int val=m_imageData[i];
35         result[i*4+1]=val;
36         result[i*4+2]=val;
37         result[i*4+3]=val;
38     }
39     // create a UIImage
40     colorSpace = CGColorSpaceCreateDeviceRGB();
41     context = CGBitmapContextCreate(result, m_width, m_height, 8, m_width * sizeof(uint32_t), colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaNoneSkipLast);
42     CGImageRef image = CGBitmapContextCreateImage(context);
43     CGContextRelease(context);
44     CGColorSpaceRelease(colorSpace);
45     UIImage *resultUIImage = [UIImage imageWithCGImage:image];
46     CGImageRelease(image);
47     // make sure the data will be released by giving it to an autoreleased NSData
48     [NSData dataWithBytesNoCopy:result length:m_width * m_height];
49     return resultUIImage;
50 }

posted on 2012-05-23 11:42 该显示名称已被其他用户使用阅读(382) 评论(0) 收藏举报