UIimage到NSData返回Null [英] UIimage to NSData returns Null

问题描述

我创建了一个二维码图像并显示在UIImageView中

  NSString * QRMessage = @MESSAGE; 
 
 NSData * data = [QRMessage dataUsingEncoding：NSISOLatin1StringEncoding allowLossyConversion：false]; 
 CIFilter * filter = [CIFilter filterWithName：@CIQRCodeGenerator]; 
 [filter setValue：data forKey：@inputMessage]; 
 [filter setValue：@QforKey：@inputCorrectionLevel]; 
 
 imageQRCode = filter.outputImage; // imageQRCode是CIImage 
 ivQR.image = [UIImage imageWithCIImage：imageQRCode]; // ivQR是UIImageView 
  

我正在尝试保存图像，以便用户可以以某种方式发送QR代码给另一个人。我首先尝试将其保存到剪贴板这样的...

  UIPasteboard * pasteBoard = [UIPasteboard pasteboardWithName：UIPasteboardNameGeneral create：没有]; 
 [pasteBoard setPersistent：true]; 
 [pasteBoard setImage：ivQR.image]; 
  

...但似乎没有任何东西保存在剪贴板中。

所以我尝试将UIImage转换为NSData，并将其添加为附件：

  MFMailComposeViewController * picker = [[MFMailComposeViewController alloc] init]; 
 picker.mailComposeDelegate = self; 
 UIImage * imageToSend = [UIImage imageWithCIImage：imageQRCode]; 
 NSData * data = UIImageJPEGRepresentation（imageToSend，1）; 
 [picker addAttachmentData：data mimeType：@image / jpegfileName：@QR.jpg]; 
  

但是似乎没有附加任何东西。

我做了一些测试，看起来我从UIImageJPEGRepresentation（）中获得的NSData给出了Null数据。该图像其实是在我的手机上显示，所以我想知道我是否只是转换数据错误？

我的大部分谷歌搜索告诉我我正在转换的方式是正确的。但大多数示例使用用户手机上的图片，或者添加到应用程序本身的图片。我的图片是创建的...所以这样做有所作为？

我的目标是允许用户复制到剪贴板或添加为附件的QR图片。

解决方案

将 CIImage 转换为 UIImage ，我发现， imageWithCIImage 通常不起作用。我通常使用 CIContext 方法 createCGImage 然后创建 UIImage 从那里：

  CIImage * ciImage = ... 
 CIContext * context = [CIContext contextWithOptions：nil]; 
 CGImageRef cgImage = [上下文createCGImage：ciImage fromRect：rect]; 
 UIImage * image = [UIImage imageWithCGImage：cgImage]; 
 CGImageRelease（cgImage）; 
  

请参阅。/ b / $ b

I created a QR code image and displayed it in a UIImageView

NSString *QRMessage = @"MESSAGE";

NSData *data = [QRMessage dataUsingEncoding:NSISOLatin1StringEncoding allowLossyConversion:false];
CIFilter *filter = [CIFilter filterWithName:@"CIQRCodeGenerator"];
[filter setValue:data forKey:@"inputMessage"];
[filter setValue:@"Q" forKey:@"inputCorrectionLevel"];

imageQRCode = filter.outputImage; // imageQRCode is CIImage
ivQR.image = [UIImage imageWithCIImage: imageQRCode]; // ivQR is UIImageView

I'm trying to save the image so the user can somehow send the QR code to another person. I first tried saving it to the "Clipboard" like this...

UIPasteboard *pasteBoard = [UIPasteboard pasteboardWithName:UIPasteboardNameGeneral create:NO];
[pasteBoard setPersistent:true];
[pasteBoard setImage:ivQR.image];

... but it appears nothing is saved in the Clipboard.

So then I tried converting the UIImage to NSData and adding it as an attachment like so:

MFMailComposeViewController *picker = [[MFMailComposeViewController alloc] init];
picker.mailComposeDelegate = self;
UIImage *imageToSend = [UIImage imageWithCIImage:imageQRCode];
NSData *data = UIImageJPEGRepresentation(imageToSend,1);
[picker addAttachmentData:data  mimeType:@"image/jpeg" fileName:@"QR.jpg"];

But again nothing seems to be attached.

I did some testing and it appears that the NSData I'm getting back from "UIImageJPEGRepresentation()" gives me "Null" data. The image does in fact get displayed on my phone, so I'm wondering if I'm just converting the data wrong?

Most of my "googling" tells me that the way I'm converting is correct. But most of the examples use a Picture on the user's phone, or a Picture added to the App itself. My Picture is "created"... so does that make a difference?

My goal is to allow the user to Copy to Clipboard, or Add as Attachment of the QR Image. Any assistance is greatly appreciated.

解决方案

When converting a CIImage to UIImage, I've found that imageWithCIImage often doesn't work. I generally use CIContext method createCGImage and then create the UIImage from that:

CIImage *ciImage     = ...
CIContext *context   = [CIContext contextWithOptions:nil];
CGImageRef cgImage   = [context createCGImage:ciImage fromRect:rect];
UIImage *image       = [UIImage imageWithCGImage:cgImage];
CGImageRelease(cgImage);

See samples in Core Image Programming Guide.

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