来自 NSURL 的 CGImage 有效但不适用于 UIImage [英] CGImage from NSURL works but not from UIImage

问题描述

我在将过滤器应用于图像时遇到了一些问题.以下代码在使用 CIImage:imageWithContentsOfURL 时完美运行:

I have some issues applying filters to an image. The following code works perfect when using CIImage:imageWithContentsOfURL:

NSInteger filterIndex = [(UITapGestureRecognizer *)sender view].tag;
Filter *filter = [filters objectAtIndex:filterIndex];

CIContext *context = [CIContext contextWithOptions:nil];

CIImage *image = [CIImage imageWithContentsOfURL:[NSURL URLWithString:@"http://url.to/photo.jpg"]];

[filter.filter setValue:image forKey:kCIInputImageKey];

CIImage *result = [filter.filter valueForKey:kCIOutputImageKey];
CGRect extent = [result extent];
CGImageRef cgImage = [context createCGImage:result fromRect:extent];

[self.imageView setImage:[UIImage imageWithCGImage:cgImage]];

Filter 只是一个包含过滤器名称和 CIFilter 的模型:

Filter is just a model holding filter name and CIFilter:

-(id)initWithNameAndFilter:(NSString *)theName filter:(CIFilter *)theFilter;
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) CIFilter *filter;

但是当我尝试使用以下代码加载本地 UIImage 时:

But when I try to load a local UIImage with the following code:

CIImage *ciImage = [UIImage imageNamed:@"test.png"].CIImage;

过滤后的图像只会变白(或消失).我做错了什么?

The filtered image only turns white (or disappears). What am I doing wrong?

推荐答案

Juraj Antas 在这个问题中的回答 如何将 UIImage 转换为 CIImage，反之亦然 解决了我的问题:

Juraj Antas' answer in this question How to Convert UIImage to CIImage and vice versa fixed my issue:

UIImage *u = [UIImage imageNamed:@"image.jpg"];
CIImage *image = [[CIImage alloc] initWithCGImage: u.CGImage];

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