1.首先得把界面转化成图片，给uiview加一个类目如下：
#import "UIView+Screen.h"
@implementation UIView (Screen)
//截取界面转化成图片
-(UIImage *)convertViewToImage
{
UIGraphicsBeginImageContext(self.bounds.size);
[self drawViewHierarchyInRect:self.bounds afterScreenUpdates:YES];
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
@end
2.得到截屏图片后进行模糊处理
给uiImage 添加一个类别方法
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。
- (UIImage *)blurredImageWithRadius:(CGFloat)radius iterations:(NSUInteger)iterations tintColor:(UIColor *)tintColor
{
//image must be nonzero size
if (floorf(self.size.width) * floorf(self.size.height) <= 0.0f) return self;
//boxsize must be an odd integer
uint32_t boxSize = (uint32_t)(radius * self.scale);
if (boxSize % 2 == 0) boxSize ++;
//create image buffers
CGImageRef imageRef = self.CGImage;
vImage_Buffer buffer1, buffer2;
buffer1.width = buffer2.width = CGImageGetWidth(imageRef);
buffer1.height = buffer2.height = CGImageGetHeight(imageRef);
buffer1.rowBytes = buffer2.rowBytes = CGImageGetBytesPerRow(imageRef);
size_t bytes = buffer1.rowBytes * buffer1.height;
buffer1.data = malloc(bytes);
buffer2.data = malloc(bytes);
//create temp buffer
void *tempBuffer = malloc((size_t)vImageBoxConvolve_ARGB8888(&buffer1, &buffer2, NULL, 0, 0, boxSize, boxSize,
NULL, kvImageEdgeExtend + kvImageGetTempBufferSize));
//copy image data
CFDataRef dataSource = CGDataProviderCopyData(CGImageGetDataProvider(imageRef));
memcpy(buffer1.data, CFDataGetBytePtr(dataSource), bytes);
CFRelease(dataSource);
for (NSUInteger i = 0; i < iterations; i++)
{
//perform blur
vImageBoxConvolve_ARGB8888(&buffer1, &buffer2, tempBuffer, 0, 0, boxSize, boxSize, NULL, kvImageEdgeExtend);
//swap buffers
void *temp = buffer1.data;
buffer1.data = buffer2.data;
buffer2.data = temp;
}
//free buffers
free(buffer2.data);
free(tempBuffer);
//create image context from buffer
CGContextRef ctx = CGBitmapContextCreate(buffer1.data, buffer1.width, buffer1.height,
8, buffer1.rowBytes, CGImageGetColorSpace(imageRef),
CGImageGetBitmapInfo(imageRef));
//apply tint
if (tintColor && CGColorGetAlpha(tintColor.CGColor) > 0.0f)
{
CGContextSetFillColorWithColor(ctx, [tintColor colorWithAlphaComponent:0.25].CGColor);
CGContextSetBlendMode(ctx, kCGBlendModePlusLighter);
CGContextFillRect(ctx, CGRectMake(0, 0, buffer1.width, buffer1.height));
}
//create image from context
imageRef = CGBitmapContextCreateImage(ctx);
UIImage *image = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
CGImageRelease(imageRef);
CGContextRelease(ctx);
free(buffer1.data);
return image;
}
此时已经拥有了模糊的背景图片，下面就简单了。
方法二 就是用coreImage中苹果提供的滤镜效果，但是此方法效率低且需要转化时相对间比较长
//CPU渲染。。慢效率低，为了避免线程阻塞，最好放在子线程里。。
- (UIImage *)blur{
CIContext *context = [CIContext contextWithOptions:nil];
CIImage *imageToBlur = [[CIImage alloc]initWithImage:_imgview.image];
CIFilter *filter = [CIFilter filterWithName:@"CIGaussianBlur" keysAndValues:kCIInputImageKey,imageToBlur ,nil];
_outputCIImage = [filter outputImage];
UIImage *img = [UIImage imageWithCGImage:[context createCGImage:_outputCIImage fromRect:_outputCIImage.extent]];
return img;
}
方法三就是用iOS8新出的功能。特别方便，还能支持实时模糊，缺点就是只能iOS8以上使用
//iOS8苹果自带的毛玻璃效果
- (IBAction)iOS8blurAction:(id)sender {
UIBlurEffect *beffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleExtraLight];
UIVisualEffectView *view = [[UIVisualEffectView alloc]initWithEffect:beffect];
view.frame = self.bounds;
[self addSubview:view];
}