關(guān)于高斯模糊的方式有很多種，但是如果需要模糊漸變，那么對(duì)這種高斯模糊算法的性能要求是比較高的，今天這里重點(diǎn)不討論算法，只是提供一個(gè)動(dòng)畫實(shí)現(xiàn)的思路。動(dòng)畫效果如下：

高斯模糊漸變動(dòng)畫

高斯模糊

-(UIImage *)boxblurImage:(UIImage *)image withBlurNumber:(CGFloat)blur
{
    if (blur < 0.f || blur > 1.f) {
      blur = 0.5f;
    }
   int boxSize = (int)(blur * 250);
    boxSize = boxSize - (boxSize % 2) + 1;
    CGImageRef img = image.CGImage;
    vImage_Buffer inBuffer, outBuffer;
    vImage_Error error;
    void *pixelBuffer;
    //從CGImage中獲取數(shù)據(jù)
    CGDataProviderRef inProvider = CGImageGetDataProvider(img);
    CFDataRef inBitmapData = CGDataProviderCopyData(inProvider);
    //設(shè)置從CGImage獲取對(duì)象的屬性
    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;
}

高斯模糊漸變

自動(dòng)漸變的過(guò)程需要加入一個(gè)定時(shí)器NSTimer,并且循環(huán)。每0.1秒循環(huán)一次，通過(guò)一個(gè)變量來(lái)計(jì)數(shù)，以改變blur值。當(dāng)然，這里的參數(shù)根據(jù)需要來(lái)調(diào)整來(lái)滿足不同的需求。

[NSTimer scheduledTimerWithTimeInterval:0.1 target:self selector:@selector(changeImageView1) userInfo:nil repeats:YES];

-(void)changeImageView1
{
    self.imageView1.image = [self boxblurImage:[UIImage imageNamed:@"login_bg_1"] withBlurNumber:self.count1/50.0];
    if (self.count1++ == 15) {
        [self.timer1 invalidate];
        self.timer1 = nil;
        self.count1 = 0;
        self.imageView2.image = [UIImage imageNamed:@"login_bg_2"];
        [UIView animateWithDuration:2 animations:^{
            self.imageView1.alpha = 0;
            self.imageView2.alpha = 1;
        } completion:^(BOOL finished) {
            [NSTimer scheduledTimerWithTimeInterval:2 target:self selector:@selector(imageView2AnimationStart) userInfo:nil repeats:NO];
        }];
    }
}

動(dòng)畫過(guò)渡

在第一張圖片模糊到一定程度時(shí)，對(duì)其做漸變處理，改變其alpha值（從1到0），同時(shí)讓第二張圖顯現(xiàn)出來(lái)（從1到0）。至此，整個(gè)動(dòng)畫就基本完成了。

另外

需要對(duì)其他方面做些優(yōu)化，比如NSTimer的開啟與暫停，以及切換到其他頁(yè)面后需要關(guān)閉定時(shí)器等。