iOS给图片添加滤镜&使用openGLES动态渲染图片详解及实例

iOS给图片添加滤镜&使用openGLES动态渲染图片
给图片增加滤镜有这两种方式: CoreImage / openGLES
下面先说明如何使用CoreImage给图片添加滤镜, 主要为以下步骤:
#1.导入CIImage格式的原始图片
#2.创建CIFilter滤镜
#3.用CIContext将滤镜中的图片渲染出来
#4.导出渲染后的图片
参考代码:

//导入CIImageCIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua"]];//创建出Filter滤镜CIFilter *filter = [CIFilter filterWithName:@"CIPixellate"];[filter setValue:ciImage forKey:kCIInputImageKey];[filter setDefaults];CIImage *outImage = [filter valueForKey:kCIOutputImageKey];//用CIContext将滤镜中的图片渲染出来CIContext *context = [CIContext contextWithOptions:nil];CGImageRef cgImage = [context createCGImage:outImagefromRect:[outImage extent]];//导出图片UIImage *showImage = [UIImage imageWithCGImage:cgImage];CGImageRelease（cgImage）;UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];imageView.center= self.view.center;[self.view addSubview:imageView];

当要设置多个滤镜的时候, 出了新创建一个CIFilter外还要额外设定kCIInputAngleKey, 代码如下:

//导入CIImageCIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua.jpeg"]];//创建出Filter滤镜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]; //如果不增加这行新增的滤镜不会生效CIImage *outputImage = [filterTwo valueForKey:kCIOutputImageKey];//用CIContext将滤镜中的图片渲染出来CIContext *context = [CIContext contextWithOptions:nil]; CGImageRef cgImage = [context createCGImage:outputImagefromRect:[outputImage extent]];//导出图片UIImage *showImage = [UIImage imageWithCGImage:cgImage];CGImageRelease（cgImage）;UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];imageView.center= self.view.center;[self.view addSubview:imageView];

下面来介绍怎么用openGLES来使用滤镜渲染图片
使用openGlES的步骤大致如下:
#1.导入要渲染的图片
#2.获取OpenGLES渲染的上下文
#3.创建出渲染的GLKView buffer
#4.创建CoreImage的上下文
#5.进行CoreImage的相关设置
#6.开始渲染并显示图片
参考代码如下:

//导入要渲染的图片UIImage *showImage = [UIImage imageNamed:@"hua.jpeg"];CGRect rect= CGRectMake（0, 0, showImage.size.width, showImage.size.height）;//获取OpenGLES渲染的上下文EAGLContext *eagContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];//创建出渲染的bufferGLKView *glkView = [[GLKView alloc] initWithFrame:rect context:eagContext];[glkView bindDrawable];[self.view addSubview:glkView];//创建出CoreImage的上下文CIContext *ciContext = [CIContext contextWithEAGLContext:eagContext options:@{kCIContextWorkingColorSpace: [NSNull null]}];//CoreImage相关设置CIImage *ciImage = [[CIImage alloc] initWithImage:showImage];CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone"];[filter setValue:ciImage forKey:kCIInputImageKey];[filter setValue:@（0） forKey:kCIInputIntensityKey];//开始渲染[ciContext drawImage:[filter valueForKey:kCIOutputImageKey] inRect:CGRectMake（0, 0, glkView.drawableWidth, glkView.drawableHeight）fromRect:[ciImage extent]];[glkView display];

如果要动态渲染, 可以通过UISilder动态调整一下代码的vaule值
[filter setValue:vaule forKey:kCIInputIntensityKey];
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