//導(dǎo)入CIImage
  CIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua"]];
  
  //創(chuàng)建出Filter濾鏡
  CIFilter *filter = [CIFilter filterWithName:@"CIPixellate"];
  
  [filter setValue:ciImage forKey:kCIInputImageKey];
  
  [filter setDefaults];
  
  CIImage *outImage = [filter valueForKey:kCIOutputImageKey];
  
  //用CIContext將濾鏡中的圖片渲染出來
  CIContext *context = [CIContext contextWithOptions:nil];
  
  CGImageRef cgImage = [context createCGImage:outImage
                    fromRect:[outImage extent]];
  
  //導(dǎo)出圖片
  UIImage *showImage = [UIImage imageWithCGImage:cgImage];
  
  CGImageRelease(cgImage);
  
  UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];
  imageView.center    = self.view.center;
  [self.view addSubview:imageView];

當(dāng)要設(shè)置多個濾鏡的時候, 出了新創(chuàng)建一個CIFilter外還要額外設(shè)定kCIInputAngleKey, 代碼如下:

//導(dǎo)入CIImage
  CIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua.jpeg"]];
  
  //創(chuàng)建出Filter濾鏡
  CIFilter *filter = [CIFilter filterWithName:@"CIPixellate"];
  
  [filter setValue:ciImage forKey:kCIInputImageKey];
  
  [filter setDefaults];
  
  CIImage *outImage = [filter valueForKey:kCIOutputImageKey];
  
  CIFilter *filterTwo = [CIFilter filterWithName:@"CIHueAdjust"];
  
  [filterTwo setValue:outImage forKey:kCIInputImageKey];
  
  [filterTwo setDefaults];
  
  [filterTwo setValue:@(1.0f) forKey:kCIInputAngleKey]; //如果不增加這行新增的濾鏡不會生效
  
  CIImage *outputImage = [filterTwo valueForKey:kCIOutputImageKey];
  
  //用CIContext將濾鏡中的圖片渲染出來
  CIContext *context = [CIContext contextWithOptions:nil]; 
  
  CGImageRef cgImage = [context createCGImage:outputImage
                    fromRect:[outputImage extent]];
  
  //導(dǎo)出圖片
  UIImage *showImage = [UIImage imageWithCGImage:cgImage];
  
  CGImageRelease(cgImage);
  
  UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];
  imageView.center    = self.view.center;
  [self.view addSubview:imageView];

下面來介紹怎么用openGLES來使用濾鏡渲染圖片

使用openGlES的步驟大致如下:

#1.導(dǎo)入要渲染的圖片

#2.獲取OpenGLES渲染的上下文

#3.創(chuàng)建出渲染的GLKView buffer

#4.創(chuàng)建CoreImage的上下文

#5.進(jìn)行CoreImage的相關(guān)設(shè)置

#6.開始渲染并顯示圖片

參考代碼如下:

//導(dǎo)入要渲染的圖片
  UIImage *showImage = [UIImage imageNamed:@"hua.jpeg"];
  CGRect rect    = CGRectMake(0, 0, showImage.size.width, showImage.size.height);
  
  //獲取OpenGLES渲染的上下文
  EAGLContext *eagContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
  
  //創(chuàng)建出渲染的buffer
  GLKView *glkView = [[GLKView alloc] initWithFrame:rect
                       context:eagContext];
  [glkView bindDrawable];
  [self.view addSubview:glkView];
  
  //創(chuàng)建出CoreImage的上下文
  CIContext *ciContext = [CIContext contextWithEAGLContext:eagContext
                           options:@{kCIContextWorkingColorSpace: [NSNull null]}];
  
  //CoreImage相關(guān)設(shè)置
  CIImage *ciImage = [[CIImage alloc] initWithImage:showImage];
  
  CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone"];
  
  [filter setValue:ciImage forKey:kCIInputImageKey];
  [filter setValue:@(0) forKey:kCIInputIntensityKey];
  
  //開始渲染
  [ciContext drawImage:[filter valueForKey:kCIOutputImageKey]
         inRect:CGRectMake(0, 0, glkView.drawableWidth, glkView.drawableHeight)
        fromRect:[ciImage extent]];
  
  [glkView display];

如果要動態(tài)渲染, 可以通過UISilder動態(tài)調(diào)整一下代碼的vaule值

[filter setValue:vaule forKey:kCIInputIntensityKey];

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