CODEWITHSUNDEEP
iphoneiosxcodegpuimage
BigAppleBump
BigAppleBump

Reputation: 1096

GPUImage change brightness with UISlider

How can i change the brightness of an Image with slider using GPUImageBrightnessFilter ?

I tried,

-(void)updateBrightness {
GPUImageFilter *selectedFilter = nil;
[selectedFilter removeAllTargets];
selectedFilter = [[GPUImageFilter alloc] init];

CGFloat midpoint = [(UISlider *)sender value];
[(GPUImageBrightnessFilter *)settingsFilter setBrightness:midpoint];        

UIImage *filteredImage = [selectedFilter imageByFilteringImage:_image_view.image];
fx_imageView.image = filteredImage;

}

Upvotes: 0

Views: 3111

Answers (2)

krushnsinh
krushnsinh

Reputation: 864

these may help you... 

-(void)viewDidLoad
{        
 [sliderChange setMinimumValue:-0.5];
 [sliderChange setMaximumValue:0.5];
 [sliderChange setValue:0.0];
 brightnessFilter = [[GPUImageBrightnessFilter alloc] init];
}
-(IBAction)upDateSliderValue:(id)sender 
{
 GPUImagePicture *fx_image;
 fx_image = [[GPUImagePicture alloc] initWithImage:originalImage];
 [brightnessFilter setBrightness:self.sliderChange.value];
 [fx_image addTarget:brightnessFilter];
 [fx_image processImage];

 UIImage *final_image = [brightnessFilter imageFromCurrentlyProcessedOutput];
 self.selectedImageView.image = final_image;  
}

Upvotes: 0

Brad Larson
Brad Larson

Reputation: 170317

There are several problems with the above code.

First, you're not actually using a brightness filter against your image, because you're calling -imageByFilteringImage: on selectedFilter, which is a generic GPUImageFilter that you allocated fresh. Your GPUImageBrightnessFilter of settingsFilter is never used.

Second, you don't want to be allocating a new filter with every time you update a parameter. Allocate your GPUImageBrightnessFilter once and simply update it as values change.

Third, you don't want to keep re-filtering UIImages. Going to and from UIImages is a slow process (and won't work properly when using -imageByFilteringImage: on the same filter, because of some caching I do). Instead, create a GPUImagePicture based on your original image, add a GPUImageBrightnessFilter to that as a target, and target your GPUImageBrightnessFilter at a GPUImageView. Use -processImage every time you update your brightness filter and your updates will be much, much faster. When you need to extract your final image, use -imageFromCurrentlyProcessedOutput.

Upvotes: 4

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