图片模糊处理

使用vImage API进行模糊
iOS5.0中新增了vImage API可以使用，它属于Accelerate.Framework，所以如果你要使用它要在工程中加入这个Framework。模糊算法使用的是vImageBoxConvolve_ARGB8888这个函数。
  1 - (UIImage *)blurredImageWithRadius:(CGFloat)radius iterations:(NSUInteger)iterations tintColor:(UIColor *)tintColor
  2 
  3 {
  4 
  5 //image must be nonzero size
  6 
  7 if (floorf(self.size.width) * floorf(self.size.height) <= 0.0f) return self;
  8 
  9 //boxsize must be an odd integer
 10 
 11 uint32_t boxSize = (uint32_t)(radius * self.scale);
 12 
 13 if (boxSize % 2 == 0) boxSize ++;
 14 
 15 //create image buffers
 16 
 17 CGImageRef imageRef = self.CGImage;
 18 
 19 vImage_Buffer buffer1, buffer2;
 20 
 21 buffer1.width = buffer2.width = CGImageGetWidth(imageRef);
 22 
 23 buffer1.height = buffer2.height = CGImageGetHeight(imageRef);
 24 
 25 buffer1.rowBytes = buffer2.rowBytes = CGImageGetBytesPerRow(imageRef);
 26 
 27 size_t bytes = buffer1.rowBytes * buffer1.height;
 28 
 29 buffer1.data = malloc(bytes);
 30 
 31 buffer2.data = malloc(bytes);
 32 
 33 //create temp buffer
 34 
 35 void *tempBuffer = malloc((size_t)vImageBoxConvolve_ARGB8888(&buffer1, &buffer2, NULL, 0, 0, boxSize, boxSize,
 36 
 37 NULL, kvImageEdgeExtend + kvImageGetTempBufferSize));
 38 
 39 //copy image data
 40 
 41 CFDataRef dataSource = CGDataProviderCopyData(CGImageGetDataProvider(imageRef));
 42 
 43 memcpy(buffer1.data, CFDataGetBytePtr(dataSource), bytes);
 44 
 45 CFRelease(dataSource);
 46 
 47 for (NSUInteger i = 0; i < iterations; i++)
 48 
 49 {
 50 
 51 //perform blur
 52 
 53 vImageBoxConvolve_ARGB8888(&buffer1, &buffer2, tempBuffer, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
 54 
 55 //swap buffers
 56 
 57 void *temp = buffer1.data;
 58 
 59 buffer1.data = buffer2.data;
 60 
 61 buffer2.data = temp;
 62 
 63 }
 64 
 65 //free buffers
 66 
 67 free(buffer2.data);
 68 
 69 free(tempBuffer);
 70 
 71 //create image context from buffer
 72 
 73 CGContextRef ctx = CGBitmapContextCreate(buffer1.data, buffer1.width, buffer1.height,
 74 
 75 8, buffer1.rowBytes, CGImageGetColorSpace(imageRef),
 76 
 77 CGImageGetBitmapInfo(imageRef));
 78 
 79 //apply tint
 80 
 81 if (tintColor && CGColorGetAlpha(tintColor.CGColor) > 0.0f)
 82 
 83 {
 84 
 85 CGContextSetFillColorWithColor(ctx, [tintColor colorWithAlphaComponent:0.25].CGColor);
 86 
 87 CGContextSetBlendMode(ctx, kCGBlendModePlusLighter);
 88 
 89 CGContextFillRect(ctx, CGRectMake(0, 0, buffer1.width, buffer1.height));
 90 
 91 }
 92 
 93 //create image from context
 94 
 95 imageRef = CGBitmapContextCreateImage(ctx);
 96 
 97 UIImage *image = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
 98 
 99 CGImageRelease(imageRef);
100 
101 CGContextRelease(ctx);
102 
103 free(buffer1.data);
104 
105 return image;
106 
107 }
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