实现图片模糊(背景虚化)

图片模糊效果

背景虚化(模糊)的效果越来越常用,那么如何使用代码来实现呢?在上篇文章中,我们讨论了关于 CoreImage 的知识,



理所当然的,首先尝试使用 CoreImage 解决问题,从上次打印出来的所有支持的滤镜中,在 127种滤镜中,存在 Blur 关键字的,只有

CIGaussianBlur

(高斯模糊),,而这种模糊的致命缺陷是,会出现白边.(懂美术的同学可能知道,这是位图和矢量图的原因)

高斯模糊代码

CIContext *context = [CIContext contextWithOptions:nil];
CIImage *inputImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"1.png"]];
// create gaussian blur filter
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:inputImage forKey:kCIInputImageKey];
[filter setValue:[NSNumber numberWithFloat:10.0] forKey:@"inputRadius"];
// blur image
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGImageRef cgImage = [context createCGImage:result fromRect:[result extent]];
UIImage *image = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);
self.mainImageView.image = image;

那么依照我现在的知识,使用 CoreImage 就没法解决问题了…

通过查找参考资料,发现 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

-(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;
}

最终效果: