iOS 渲染图片 CIFilter

一、首先来创建一下滑动条吧！

- (void)addSlider {
    
    for (int i = 0; i < self.chooseArray.count; i++) {
        
        UISlider *slider = [[UISlider alloc] initWithFrame:CGRectMake((kScreenWidth-200)/2, kScreenHeight-180, 200, 30)];
        [slider addTarget:self action:@selector(beautifyImage:) forControlEvents:UIControlEventValueChanged];
        slider.hidden = YES;
        slider.tag = 51000 + i;
        slider.maximumValue = 100;
        if (i == 3) {
            
            slider.minimumValue = 0;
            slider.value = 0;
        } else if (i == 5) {
            
            slider.minimumValue = 0;
            slider.value = 0;
        } else if (i == 6) {
            
            slider.minimumValue = 0;
            slider.value = 100;
        } else {
            
            slider.minimumValue = -100;
            slider.value = 0;
        }
        [self.view addSubview:slider];
        [self.sliderArray addObject:slider];
    }
}```

二、根据slider调节

• (void)beautifyImage:(UISlider *)slider {

  self.inputImage = [CIImage imageWithCGImage:self.showImage.CGImage];
  CIFilter *filter = nil;

  NSInteger index = slider.tag - 51000;
  if (index == 0 || index == 1 || index == 2) {

    filter = [CIFilter filterWithName:@"CIColorControls"];
  

  } else if (index == 3) {

    filter = [CIFilter filterWithName:@"CISepiaTone"];
  

  } else if (index == 4){

    filter = [CIFilter filterWithName:@"CIHueAdjust"];
  

  } else if (index == 5) {

    filter = [CIFilter filterWithName:@"CIGaussianBlur"];
  

  } else if (index == 6) {

    filter = [CIFilter filterWithName:@"CIHighlightShadowAdjust"];
  

  }
  [filter setValue:self.inputImage forKey:kCIInputImageKey];

switch (index) {
    //亮度   -1---1 默认为0
    case 0: {
        [filter setValue:[NSNumber numberWithFloat:(slider.value/200)] forKey:@"inputBrightness"];
    }
        break;
        //对比度   0---4 默认为1
    case 1: {
        
        CGFloat value = 0;
        if (slider.value <= 0) {
            
            value = (slider.value + 100)/200 + 0.5;
        } else {
            
            value = (slider.value + 50)/100 + 1;
        }
        [filter setValue:[NSNumber numberWithFloat:value] forKey:@"inputContrast"];
    }
        break;
        //饱和度      0---2 默认为1
    case 2: {
        
        CGFloat value = 0;
        if (slider.value < 0) {
            
            value = (slider.value + 100) / 200 + 0.5;
        } else if (slider.value > 0) {
            
            value = (slider.value / 200) + 1;
        }
        [filter setValue:[NSNumber numberWithFloat:value] forKey:@"inputSaturation"];
    }
        break;
        //色温    0 -- 1 默认为1
    case 3: {
        
        [filter setValue:[NSNumber numberWithFloat:slider.value/200] forKey:@"inputIntensity"];
    }
        break;
        //色调  -3.14 -- 3.14 默认为0
    case 4: {
        [filter setValue:[NSNumber numberWithFloat:(slider.value * M_PI)/500] forKey:@"inputAngle"];
    }
        break;
        //模糊 0 -- 100 默认为10
    case 5: {
        [filter setValue:[NSNumber numberWithFloat:slider.value/50] forKey:@"inputRadius"];
    }
        break;
        //高亮  0.3 -- 1 默认为1
    case 6: {
        [filter setValue:[NSNumber numberWithFloat:(slider.value / 200 + 0.5)] forKey:@"inputHighlightAmount"];
    }
        break;
    default:
        return;
}

NSString *name = self.chooseArray[index];
self.valueLabel.text = [NSString stringWithFormat:@"%@ %1.f",name,slider.value];
// 转换图片, 创建基于GPU的CIContext对象
CIContext *context = [CIContext contextWithOptions: nil];
// 得到过滤后的图片
CIImage *outputImage = [filter valueForKey:kCIOutputImageKey];
CGImageRef cgimg = [context createCGImage:outputImage fromRect:[outputImage extent]];
UIImage *newImage = [UIImage imageWithCGImage:cgimg];

//显示图片的ImageView
self.showImageView.image = newImage;
//    self.inputImage = outputImage;
// 释放C对象
CGImageRelease(cgimg);

}```

三、如何查看CIFilter的所有属性？

- (void)showFilertName {
    
    NSArray *cifilter = [CIFilter filterNamesInCategory:kCICategoryBuiltIn];
    
    NSLog(@"FilterName:\n%@,,,===%ld", cifilter,cifilter.count);//显示所有过滤器名字
    
   for (NSString *filterName in cifilter) {
    
    CIFilter *fltr = [CIFilter filterWithName:filterName];    
    //用一个过滤器名字生成一个过滤器CIFilter对象
    NSLog(@":\n%@", [fltr attributes]);
        }
}```