ios - 如何将 CIFilter 应用于 UIImage？

Question

当我尝试将滤镜应用到用户选择的 UIImage 时，我的应用程序崩溃了(在不应用滤镜的情况下它一直运行良好)。我将“CoreImage”框架添加并导入到我的项目中，这样我就可以为用户选择的图像创建过滤器。

我试图通过为 UIImage 创建一个类别(基于 Apple's documentation ，然后在用户选择的 UIImage 上调用相应的方法来应用过滤器. 以下是我的类别标题和主体的代码；我做错了什么？(请注意，“randColor”是类别 UIColor 类方法，用于生成随机颜色)

#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

这是 viewController 中调用该类别的方法:

- (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

我想通了!在调试并使用其他一些项目作为引用点之后，我意识到我遇到了两个问题。首先，我试图为 CIColor 使用 UIColor，这不可能直接实现。我首先必须将 UIColor 转换为 CIColor 才能应用它。接下来，我没有为 CIFilter 值键使用正确的字符串。以下是修改后的代码(现在可以使用了!)

#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