从包含 CGImage 的 UIImage 对象获取 NSData [英] Getting NSData from UIImage object that contains CGImage

问题描述

为了将图像文件上传到我的服务器，我需要获取它的 NSData.我现在无法执行此操作，因为我的 UIImage 包含一个 CGImage.

In order to upload an image file to my server, I need to get it's NSData. I am having trouble doing this right now, because my UIImage contains a CGImage.

让我向您展示我是如何做事的.当用户拍照时，这就是我对拍摄的照片所做的:

Let me show you how I am doing things. When a user takes a photo, this is what I do with the captured photo:

NSData *imageData = [AVCaptureStillImageOutput jpegStillImageNSDataRepresentation:imageDataSampleBuffer];


UIImage *image = [[UIImage alloc]initWithData:imageData];


   _subLayer = [CALayer layer];


      image = [self selfieCorrection:image];


      image = [self rotate:image andOrientation:image.imageOrientation];


          CGRect cropRectFinal = CGRectMake(cropRect.origin.x, 140, cropRect.size.width, cropRect.size.height);

          CGImageRef imageRef = CGImageCreateWithImageInRect([image CGImage], cropRectFinal);


_subLayer.contents = (id)[UIImage imageWithCGImage:imageRef].CGImage;

在上面的代码中，我创建了一个 UIImage，并用 imageData 对象初始化它.我还创建了一个名为 _subLayer 的图层对象，它将在屏幕上显示最终图像.然后旋转和校正图像的方向，然后我设置一个 CGRect 来裁剪我想要保留的图像部分.

In the above code, I create a UIImage, and initialize it with the imageData object. I also create a layer object called _subLayer that will display the final image on the screen. The image's orientation is then rotated and corrected, and then I setup a CGRect to crop the part of the image I want to keep.

最重要的部分是最后 2 条语句.我使用原始 UIImage 创建了一个名为 imageRef 的 CGImageRef.然后，在最后一个语句中，我将 _subLayer 的内容属性设置为等于我的最终图像.

The most important part are the last 2 statements. I create a CGImageRef called imageRef using the original UIImage. Then, in the last statement, I set the contents property of _subLayer to equal my final image.

在同一个视图控制器的更深处，在 IBAction 内部，我有以下语句可以帮助我将图像传递给我的下一个视图控制器:sendFriendsVC.finalPhotoToSend = _subLayer.contents;

A little further down in this same view controller, inside of an IBAction I have the following statement which helps me pass the image to my next view controller: sendFriendsVC.finalPhotoToSend = _subLayer.contents;

finalPhotoToSend 是我在下一个视图控制器的头文件中设置的属性，如下所示:

finalPhotoToSend is a property that I have setup in the header file of my next view controller like this:

@property (nonatomic, retain) UIImage *finalPhotoToSend;

当我转到下一个视图控制器时，数据成功传递，但是当我使用 NSLog finalPhotoToSend 时，即使它是一个 UIImage，它也会这样打印到控制台:

The data is successfully passed when I segue to the next view controller, but when I NSLog finalPhotoToSend, even though it is a UIImage, it prints as this to the console:

<CGImage 0x1563dac0>

为了将照片上传到我的后端服务器服务，我需要使用 NSData 创建一个对象.我尝试使用这 2 种方法从 finalPhotoToSend 对象中获取 NSData:

In order to upload photos to my backend server service, it requires me to create an object using NSData. I have tried using these 2 methods to get the NSData out of the finalPhotoToSend object:

NSData *imageData = UIImageJPEGRepresentation(finalPhotoToSend, 0.7);

和

NSData *imageData = UIImagePNGRepresentation(finalPhotoToSend);

但那些总是在 xcode 中给我以下错误:

But those always give me the following error in xcode:

NSInvalidArgumentException', reason: '-[__NSCFType CGImage]: unrecognized selector sent to instance

我不知道该怎么做.我应该使用不同的方法从 UIImage 中获取 NSData，因为它在技术上持有 CGImage?在将数据传递给下一个视图控制器之前，我是否应该做一些不同的事情?

I am not sure what to do. Is there a different method I should be using to get NSData out of my UIImage since it is technically holding a CGImage? Should I be doing something differently before I even pass the data to my next view controller?

为迈克尔

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:self {


    if ([segue.identifier isEqualToString:@"mediaCaptureToSendToFriendsSegue"]) {


    SendToFriendsViewController *sendFriendsVC = segue.destinationViewController;


        sendFriendsVC.finalPhotoToSend = _subLayer.contents;


    }
}

推荐答案

更好的答案:

您需要真正将 UIImage 对象(而不是 CGImage 指针)设置为您已声明为 UIImage 对象的属性.

You need to truly set a UIImage object (and not a CGImage pointer) to a property that you've declared to be a UIImage object.

原文:

如果finalPhotoToSend"是一个属性，你应该这样做:

if "finalPhotoToSend" is a property, you should be doing:

NSData *imageData = UIImageJPEGRepresentation(self.finalPhotoToSend, 0.7);

而不是:

NSData *imageData = UIImageJPEGRepresentation(finalPhotoToSend, 0.7);

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