如何将CIFilter应用于UIImage？

Question

当我尝试将过滤器应用于我的用户选择时,我的应用程序崩溃了UIImage(它在没有应用过滤器的情况下工作正常).我添加了"CoreImage"框架并将其导入到我的项目中,因此我可以为用户选择的图像创建过滤器.

我试图通过创建一个类别UIImage(基于Apple的文档,然后调用UIImage用户选择的相应方法)来应用过滤器.以下是我的类别标题和正文的代码;我做错了什么？(请请注意,"randColor"是一种UIColor生成随机颜色的类别类方法

#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

以下是viewController调用此类别的方法:

- (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];

    }];
}

Answer 1

我想到了!在调试并使用其他一些项目作为参考之后,我意识到我遇到了两个问题.首先,我试图使用UIColor进行CIColor,这不是直接可行的.我首先必须将UIColor转换为CIColor以便能够应用它.接下来,我没有使用正确的字符串作为CIFilter值键.以下是修改后的代码(现在可以使用!)

#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