App设计时往往会用到一些模糊效果。iOS目前已提供一些模糊API可以让我们方便是使用。一种是使用Core Image，另一种是使用Accelerate.Framework中的vImage API。
使用Core Image进行模糊
Core Image很早在Mac系统中得到应用，后来这个Framework也开始应用到iOS，不过直到iOS6.0才开始支持模糊。这个API调用起来很方便简洁。
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- (UIImage *)blurryImage:(UIImage *)image
withBlurLevel:(CGFloat)blur {
CIImage *inputImage = [CIImage imageWithCGImage:image.CGImage];
CIFilter *filter = [CIFilter filterWithName:
@"CIGaussianBlur"
keysAndValues:kCIInputImageKey, inputImage,
@"inputRadius"
, @(blur),
nil
];
CIImage *outputImage = filter.outputImage;
CGImageRef outImage = [
self
.context createCGImage:outputImage
fromRect:[outputImage extent]];
return
[UIImage imageWithCGImage:outImage];
}
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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。
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- (UIImage *)blurryImage:(UIImage *)image withBlurLevel:(CGFloat)blur {
if
(blur < 0.f || blur > 1.f) {
blur = 0.5f;
}
int
boxSize = (
int
)(blur * 100);
boxSize = boxSize - (boxSize % 2) + 1;
CGImageRef img = image.CGImage;
vImage_Buffer inBuffer, outBuffer;
vImage_Error error;
void
*pixelBuffer;
CGDataProviderRef inProvider = CGImageGetDataProvider(img);
CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
inBuffer.width = CGImageGetWidth(img);
inBuffer.height = CGImageGetHeight(img);
inBuffer.rowBytes = CGImageGetBytesPerRow(img);
inBuffer.data = (
void
*)CFDataGetBytePtr(inBitmapData);
pixelBuffer = malloc(CGImageGetBytesPerRow(img) *
CGImageGetHeight(img));
if
(pixelBuffer ==
NULL
)
NSLog
(
@"No pixelbuffer"
);
outBuffer.data = pixelBuffer;
outBuffer.width = CGImageGetWidth(img);
outBuffer.height = CGImageGetHeight(img);
outBuffer.rowBytes = CGImageGetBytesPerRow(img);
error = vImageBoxConvolve_ARGB8888(&inBuffer,
&outBuffer,
NULL
,
0,
0,
boxSize,
boxSize,
NULL
,
kvImageEdgeExtend);
if
(error) {
NSLog
(
@"error from convolution %ld"
, error);
}
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef ctx = CGBitmapContextCreate(
outBuffer.data,
outBuffer.width,
outBuffer.height,
8,
outBuffer.rowBytes,
colorSpace,
kCGImageAlphaNoneSkipLast);
CGImageRef imageRef = CGBitmapContextCreateImage (ctx);
UIImage *returnImage = [UIImage imageWithCGImage:imageRef];
//clean up
CGContextRelease(ctx);
CGColorSpaceRelease(colorSpace);
free(pixelBuffer);
CFRelease(inBitmapData);
CGColorSpaceRelease(colorSpace);
CGImageRelease(imageRef);
return
returnImage;
}
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