iPhone iOS saving data obtained from UIImageJPEGRepresentation() fails second time: ImageIO: CGImageRead_mapData 'open' failed
ios, iphone, javax.imageio, objective-c, uiimage
Solution
I've run into something similar before. It looked like `imageWithContentsOfFile` kept the file open as long as the `UIImage` it was used to create was still alive. At the time, I had gotten around the problem by reading the file into a `NSData` and then creating the `UIImage` from the `NSData` instead of the file directly.
Problem
I'm running into a weird issue with my UIImage manipulation. I'm doing a dropbox sync, and have to store my images as local files. To do so, I save them using the `UIImagePNGRepresentation(image)` or `UIImageJPEGRepresentation(image, 0.66)` Here's my typical workflow: User selects an image or takes a photo Image gets assigned to an imageView The image view's UIImage gets saved to a file using the method below Next time the user re-opens the app, I read the image back from the file using ``` [UIImage imageWithContentsOfFile:fullImagePath] ``` This works once. The second time I run through the routine, I get the error message listed below when trying to save the image to disk once again. ``` //saving the image NSData* data = isPNG?UIImagePNGRepresentation(image):UIImageJPEGRepresentation(image, 0.66); BOOL success = [data writeToFile:filepath atomically:YES]; if(!success) { DLog(@"failed to write to file: %@",filepath ); } //loading the image [UIImage imageWithContentsOfFile:fullImagePath] ``` I'm getting this error when I try to re-save an image that has been previously converted to JPEG or PNG ``` 2012-05-21 08:16:06.680 file already exists: NO ImageIO: CGImageRead_mapData 'open' failed '/var/mobile/Applications/C1312BF8-C648-4397-82F3-D93E4FAAD35F/Documents/imageData/LogoImage.jpg' error = 2 (No such file or directory) May 21 08:16:06 <Error>: ImageIO: JPEG Not a JPEG file: starts with 0xff 0xd9 May 21 08:16:06 <Error>: ImageIO: JPEG Application transferred too few scanlines ``` It appears to me that this error is happening due to me trying to re-save the image as JPEG once again. If I ask the view to render itself in context (effectively creating a new image), the error does not happen. Does anyone know what I'm doing wrong? Am I missing some kind of metadata by trying to convert a UIImage to data, reloading it, and trying to convert it once again after displaying it to the user?