iOS的模糊效果实现方法有好几种，基本分为两种方式，一种是将图片进行模糊，一种是将模糊的控件放在UI界面上，使控件覆盖的区域达到模糊的效果。每种方式我各选了2种方法，下面介绍一下它们的实现方式以及对比一下它们的优缺点。
屏幕快照 2016-07-29 上午10.10.32.png
coreImage
该方法实现的模糊效果较好，模糊程度的可调范围很大，可以根据实际的需求随意调试。缺点就是耗时，我在模拟器上跑需要1-2秒的时间，所有该方法需要放在子线程中执行。
dispatch_async(dispatch_get_global_queue(0, 0), ^{
CIContext *context = [CIContext contextWithOptions:nil];
CIImage *ciImage = [CIImage imageWithCGImage:image.CGImage];
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur"];
[filter setValue:ciImage forKey:kCIInputImageKey];
//设置模糊程度
[filter setValue:@30.0f forKey: @"inputRadius"];
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGRect frame = [ciImage extent];
NSLog(@"%f,%f,%f,%f",frame.origin.x,frame.origin.y,frame.size.width,frame.size.height);
CGImageRef outImage = [context createCGImage: result fromRect:ciImage.extent];
UIImage * blurImage = [UIImage imageWithCGImage:outImage];
dispatch_async(dispatch_get_main_queue(), ^{
coreImgv.image = blurImage;
});
});
vImage
该方法效率高，但是模糊程度最大只能达到上图展示的程度，而且我在使用它对网络加载的图片进行模糊时，整个图片会变红。
//使用前需要导入头文件
#import <Accelerate/Accelerate.h>
+ (UIImage *)boxblurImage:(UIImage *)image withBlurNumber:(CGFloat)blur {
if (blur < 0.f || blur > 1.f) {
blur = 0.5f;
}
int boxSize = (int)(blur * 40);
boxSize = boxSize - (boxSize % 2) + 1;
CGImageRef img = image.CGImage;
vImage_Buffer inBuffer, outBuffer;
vImage_Error error;
void *pixelBuffer;
//从CGImage中获取数据
CGDataProviderRef inProvider = CGImageGetDataProvider(img);
CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
//设置从CGImage获取对象的属性
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;
}
下面两种方法实现起来都很简单，但是只有几种系统提供的样式可选。
BlurEffect是在iOS8之后才出现的，它和toolbar实现的效果基本一样，比toolbar多了一种颜色更深的样式，如上面大图所示。
BlurEffect
UIImageView *blurImgv = [[UIImageView alloc]initWithFrame:CGRectMake(50, 500, 150, 150)];
blurImgv.image = image;
[self.view addSubview:blurImgv];
UIBlurEffect *beffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];
UIVisualEffectView *view = [[UIVisualEffectView alloc]initWithEffect:beffect];
view.frame = blurImgv.frame;
[self.view addSubview:view];
toolbar
UIImageView *toolImgv = [[UIImageView alloc]initWithFrame:CGRectMake(210, 500, 150, 150)];
toolImgv.image = image;
[self.view addSubview:toolImgv];
UIToolbar *toolBar = [[UIToolbar alloc]initWithFrame:CGRectMake(210, 500, 150, 150)];
toolBar.barStyle = UIBarStyleDefault;
[self.view addSubview:toolBar];
上面介绍了四种实现模糊效果的方法，同时也进行了简单的比较。具体的使用还是要根据项目的需求选择最合适的方法。
