My app is crashing when I attempt to apply a filter to my user-selected UIImage
(It has been working fine without applying the filter). I added and imported the "CoreImage" framework to my project so I could create filters for user-selected images.
I am attempting to apply the filter by creating a category for UIImage
(based on Apple's documentation, and then calling the corresponding method on the UIImage
selected by the user. Following is the code of my category header and body; what am I doing wrong? (please note, "randColor" is a category UIColor
class method to generate a random color)
#import <UIKit/UIKit.h>
#import <CoreImage/CoreImage.h>
#import "UIColor+CustomColorCategory.h"
@interface UIImage (MonoChromeFilter)
- (UIImage *) applyMonoChromeWithRandColor;
@end
#import "UIImage+MonoChromeFilter.h"
@implementation UIImage (MonoChromeFilter)
- (UIImage *)applyMonoChromeWithRandColor
{
CIContext *context = [CIContext contextWithOptions:nil];
CIImage *ciImage = [[CIImage alloc] initWithImage:self];
CIFilter *filter = [CIFilter filterWithName:@"CIColorMonochrome"];
[filter setValue:ciImage forKey:kCIInputImageKey];
[filter setValue:[UIColor randColor] forKey:kCIAttributeTypeColor];
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGRect extent = [result extent];
CGImageRef cgImage = [context createCGImage:result fromRect:extent];
UIImage *filteredImage = [[UIImage alloc] initWithCGImage:cgImage];
return filteredImage;
}
@end
Here is the method in the viewController
where this category is being called:
- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
[picker dismissViewControllerAnimated:YES completion:^{
UIImage *editedImage = [info objectForKey:UIImagePickerControllerEditedImage];
editedImage = [editedImage applyMonoChromeWithRandColor];
self.blogImageOutlet.image = editedImage;
self.blogImageOutlet.layer.cornerRadius = self.blogImageOutlet.frame.size.width / 2.0;
[self.blogImageOutlet setClipsToBounds:YES];
[self saveImageToLibrary:editedImage];
}];
}
I figured it out! After debugging and using some other projects as a point of reference, I realized that I was experiencing two issues. First, I was trying to use a UIColor for CIColor, which is not directly possible. I first had to covert the UIColor to a CIColor to be able to apply it. Next, I was not using the correct strings for the CIFilter value keys. Here is the following code after modifications (and now it works!)
#import "UIImage+MonoChromeFilter.h"
@implementation UIImage (MonoChromeFilter)
+ (UIImage *) applyMonoChromeWithRandColor: (UIImage *)uIImage
{
// Convert UIColor to CIColor
CGColorRef colorRef = [UIColor randColor].CGColor;
NSString *colorString = [CIColor colorWithCGColor:colorRef].stringRepresentation;
CIColor *coreColor = [CIColor colorWithString:colorString];
CIContext *context = [CIContext contextWithOptions:nil];
// Convert UIImage to CIImage
CIImage *ciImage = [[CIImage alloc] initWithImage:uIImage];
// Set values for CIColorMonochrome Filter
CIFilter *filter = [CIFilter filterWithName:@"CIColorMonochrome"];
[filter setValue:ciImage forKey:kCIInputImageKey];
[filter setValue:@1.0 forKey:@"inputIntensity"];
[filter setValue:coreColor forKey:@"inputColor"];
CIImage *result = [filter valueForKey:kCIOutputImageKey];
CGRect extent = [result extent];
CGImageRef cgImage = [context createCGImage:result fromRect:extent];
UIImage *filteredImage = [[UIImage alloc] initWithCGImage:cgImage];
return filteredImage;
}
@end