在iOS 9.1中从前台和后台的资产图像接收到不同的数据大小？

Question

I want to take backup of images on cloud so I calculate MD5 of an image in iOS.The issue is Md5 differs when it is calculated in foreground and background of the app. This issue come only in iOS 9.1. I use asset library to fetch the images. Below function is used to get the data (Both data are different from each when the application is in foreground and in background)

ALAssetRepresentation *assetRep = [asset defaultRepresentation];

CGImageRef imgRef = [assetRep fullScreenImage];
UIImage *img = [UIImage imageWithCGImage:imgRef
                                   scale:1.0f
                             orientation:(UIImageOrientation)assetRep.orientation];

NSData *data = UIImageJPEGRepresentation(img, 90);

Thanks in advance....

Answer 1

Have a look at ALAssetRepresentation-MD5 which calculates the md5 hash from an ALAssetRepresentation without creating a UIImage or using UIImageJPEGRepresentation . I assume that one of these UIKit -related steps is responsible for your issue, event though they should be thread-safe.