iOS Add Filter to Picture Using openGLES Dynamic Rendering Picture Details and Examples

  • 2021-06-28 14:15:05
  • OfStack

iOS Add Filters to Pictures & Render pictures dynamically using openGLES

There are two ways to add a filter to a picture: CoreImage / openGLES

The following steps explain how to use CoreImage to add a filter to a picture:

#1. Import the original picture in CIImage format

#2. Create CIFilter filters

Render #3. Render the image in the filter with CIContext

Render #4. Export rendered pictures

Reference code:


// Import CIImage
  CIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua"]];
  
  // Create Filter Filters 
  CIFilter *filter = [CIFilter filterWithName:@"CIPixellate"];
  
  [filter setValue:ciImage forKey:kCIInputImageKey];
  
  [filter setDefaults];
  
  CIImage *outImage = [filter valueForKey:kCIOutputImageKey];
  
  // use CIContext Render pictures in filters 
  CIContext *context = [CIContext contextWithOptions:nil];
  
  CGImageRef cgImage = [context createCGImage:outImage
                    fromRect:[outImage extent]];
  
  // Export Pictures 
  UIImage *showImage = [UIImage imageWithCGImage:cgImage];
  
  CGImageRelease(cgImage);
  
  UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];
  imageView.center    = self.view.center;
  [self.view addSubview:imageView];

When multiple filters are set, an extra kCIInputAngleKey is added to the new CIFilter.


// Import CIImage
  CIImage *ciImage = [[CIImage alloc] initWithImage:[UIImage imageNamed:@"hua.jpeg"]];
  
  // Create Filter Filters 
  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]; // If you don't add this new line of filters, they won't work 
  
  CIImage *outputImage = [filterTwo valueForKey:kCIOutputImageKey];
  
  // use CIContext Render pictures in filters 
  CIContext *context = [CIContext contextWithOptions:nil]; 
  
  CGImageRef cgImage = [context createCGImage:outputImage
                    fromRect:[outputImage extent]];
  
  // Export Pictures 
  UIImage *showImage = [UIImage imageWithCGImage:cgImage];
  
  CGImageRelease(cgImage);
  
  UIImageView *imageView = [[UIImageView alloc] initWithImage:showImage];
  imageView.center    = self.view.center;
  [self.view addSubview:imageView];

Here's how to use openGLES to render pictures using filters

The steps for using openGlES are as follows:

Render #1. Import pictures to render

Rendering #2. Get context for OpenGLES rendering

Render #3. Create Rendered GLKView buffer

#4. Create context for CoreImage

#5. Set up CoreImage

Render #6. Start rendering and display pictures

The reference code is as follows:


// Import pictures to render 
  UIImage *showImage = [UIImage imageNamed:@"hua.jpeg"];
  CGRect rect    = CGRectMake(0, 0, showImage.size.width, showImage.size.height);
  
  // Obtain OpenGLES Rendered Context 
  EAGLContext *eagContext = [[EAGLContext alloc] initWithAPI:kEAGLRenderingAPIOpenGLES2];
  
  // Create rendered buffer
  GLKView *glkView = [[GLKView alloc] initWithFrame:rect
                       context:eagContext];
  [glkView bindDrawable];
  [self.view addSubview:glkView];
  
  // Create CoreImage Context 
  CIContext *ciContext = [CIContext contextWithEAGLContext:eagContext
                           options:@{kCIContextWorkingColorSpace: [NSNull null]}];
  
  //CoreImage Related Settings 
  CIImage *ciImage = [[CIImage alloc] initWithImage:showImage];
  
  CIFilter *filter = [CIFilter filterWithName:@"CISepiaTone"];
  
  [filter setValue:ciImage forKey:kCIInputImageKey];
  [filter setValue:@(0) forKey:kCIInputIntensityKey];
  
  // Start Rendering 
  [ciContext drawImage:[filter valueForKey:kCIOutputImageKey]
         inRect:CGRectMake(0, 0, glkView.drawableWidth, glkView.drawableHeight)
        fromRect:[ciImage extent]];
  
  [glkView display];

If you want to render dynamically, you can adjust the vaule value of the code under 1 dynamically by UISilder

[filter setValue:vaule forKey:kCIInputIntensityKey];

Thank you for reading, I hope to help you, thank you for your support on this site!


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