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CIImage
    CIImage *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:outImage
                                       fromRect:[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];

滤镜有哪些可选可以参看以下文章:http://www.jianshu.com/p/3e2cca585ccc

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CIImage
    CIImage *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:outputImage
                                       fromRect:[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buffer
    GLKView *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];