GPUImage简单的图片亮度调节

前言

这两天在研究如何利用UISlider来调节图片的亮度，这里给出两个版本，一种是将亮度设定死，第二种是可以利用UISlider来调节亮度，仅供初学者们一起探讨交流。

一 将亮度设定死：

- (void)brightness1{
//    目标图片
    UIImage *image = [UIImage imageNamed:@"placeholder"];
    
    //    1.在GPUImageBrightnessFilter中首先初始化该滤镜
    GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc] init];
    //    2.设置亮度值为0.5
    brightnessFilter.brightness = 0.5;
    //    3.设置亮度调整范围为整张图像
    [brightnessFilter forceProcessingAtSize:image.size];
    [brightnessFilter useNextFrameForImageCapture];
    
    
    //    4.获取数据源
    GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image];
    //    5.添加上滤镜
    [pic addTarget:brightnessFilter];
    //    6.处理图像，开始渲染
    [pic processImage];
    
    NSLog(@"Hello World");
    //    7.获取处理后的图像
    UIImage *imageBrightness = [brightnessFilter imageFromCurrentFramebuffer];
    
    //    8.加载出来
    UIImageView *imageView = [[UIImageView alloc] init];
    imageView.image = imageBrightness;
    imageView.frame = CGRectMake(0, 0, imageBrightness.size.width, imageBrightness.size.height);
    
    [self.view addSubview:imageView];
}

二 利用UISlider来调节亮度：

@interface ViewController ()
//数据源，用强引用
@property (nonatomic, strong) GPUImagePicture *pic;
//亮度滤镜
@property (nonatomic, weak) GPUImageBrightnessFilter *brightnessFilter;

@end


@implementation ViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    
    [self brightness2];
    
}


- (void)brightness2{
    
    UIImage *image = [UIImage imageNamed:@"placeholder"];
    
//    在GPUImageBrightnessFilter中首先初始化该滤镜
    GPUImageBrightnessFilter *brightnessFilter = [[GPUImageBrightnessFilter alloc] init];
    _brightnessFilter = brightnessFilter;

//    设置亮度调整范围为整张图像
    [brightnessFilter forceProcessingAtSize:image.size];
    [brightnessFilter useNextFrameForImageCapture];
    
    
//    获取数据源
    GPUImagePicture *pic = [[GPUImagePicture alloc] initWithImage:image smoothlyScaleOutput:YES];
    _pic = pic;
    
    
//    创建最终预览的view
    GPUImageView *gpuView = [[GPUImageView alloc] initWithFrame:[UIScreen mainScreen].bounds];
    [self.view insertSubview:gpuView atIndex:0];
//    设置GPUImage响应链，从数据源 => 滤镜 => 最终界面效果
    [pic addTarget:brightnessFilter]; //   ① 添加上滤镜
    [brightnessFilter addTarget:gpuView]; // ② 添加效果界面

//    创建slider
    UISlider *slider = [[UISlider alloc] initWithFrame:CGRectMake(25.0, [UIScreen mainScreen].bounds.size.height - 190, [UIScreen mainScreen].bounds.size.width - 50.0, 40.0)];
    [slider addTarget:self action:@selector(updateSliderValue:) forControlEvents:UIControlEventValueChanged];
    slider.autoresizingMask = UIViewAutoresizingFlexibleWidth | UIViewAutoresizingFlexibleTopMargin;
    slider.minimumValue = 0.0;
    slider.maximumValue = 1.0;
    slider.value = 0.0;
    
    [gpuView addSubview:slider];
    //    设置亮度值。
    brightnessFilter.brightness = slider.value;
    //    数据源处理图像，开始渲染
    [pic processImage];
}

- (void)updateSliderValue:(UISlider *)sender
{
    _brightnessFilter.brightness = sender.value;
//    数据源，给我重新处理下图片
    [_pic processImage];
}

}

这两个方案的区别在于，想利用slider来动态调节图片亮度，那么这里就必须用到GPUImageView来预览最终的效果了，不能直接用UIImageView。

参考资料：
http://blog.csdn.net/sinat_30162391/article/details/51085651
http://www.cnblogs.com/salam/p/5118704.html
http://www.cnblogs.com/qianyindichang/p/4023717.html
http://www.jianshu.com/p/4646894245ba