Objective c 将CIFilter应用于图像会生成空UIImage

我正在尝试对从UIImagePickerController接收的图像应用CIFilter。以下是我正在使用的代码：

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    [picker dismissViewControllerAnimated:YES completion:nil];

    UIImage *userImage = info[UIImagePickerControllerOriginalImage];
    UIImage *croppedImage = [UIImage imageWithCGImage:CGImageCreateWithImageInRect(userImage.CGImage, CGRectMake(0, 320, 640, 640))];

    CIContext *context = [CIContext contextWithOptions:nil];
    CIImage *img = [CIImage imageWithCGImage:croppedImage.CGImage];
    CIFilter *adjustFilter = [CIFilter filterWithName:@"CILineOverlay"];

    [adjustFilter setDefaults];
    [adjustFilter setValue:img forKey:kCIInputImageKey];
    [adjustFilter setValue:[NSNumber numberWithFloat:1.0] forKey:@"inputNRSharpness"];
    CIImage *adjustedImage = [adjustFilter valueForKey:kCIOutputImageKey];
    UIImage *newImage = [UIImage imageWithCIImage:[context createCGImage:adjustedImage fromRect:adjustedImage.extent]];

    NSLog(@"%@", newImage);

    self.myImageView.image = newImage;

}

现在，当应用过滤器的过程完成时，不会出现错误，尽管控制台会记录，但在图像视图中看不到图像。如果我跳过处理部分，只将未过滤的裁剪图像指定给图像视图，它将显示良好

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那么我做错了什么？我想用这段代码来处理一个屏幕截图，但我用一张照片试过了，结果还是一样的零。

在iOS中还没有。这有一个开源库，请尝试这3个过滤器，它可能会对您有所帮助！1 GPUImageCrosshatchFilter 2 GPUImageSketchFilter 3 GPUImageToonFilter