On the iPhone I saved an image to the photo library with modifications (appending data after the image code) using the assest library to save the NSData directly to the photo library. Now I want to read the image back from the photo library as an NSData to read it. If I read it as a UIImage, it changes the data inside the image.
How can I read the photo from the photo library as NSData? I tried looking into the reference URL in 4.1 but no luck.
Edit: I edited to explain why I'm saving it as an NSData. The URL method in the answers works if you just want pure NSData, but does not help in the context that I am asking.
Edit 2: The answer with the getBytes was the answer that did it for me. The code I used was:
int8_t *bytes = malloc([representation size]);
NSUInteger length = [representation getBytes:bytes fromOffset:0 length:[representation size] error:&error];
This was able to get me everything inside the file which gave me the image code PLUS what I added in NSData form.
Edit 3:
Is there a way to do this now in iOS 10 with the PHPhotoLibrary which replaces AssetLibrary? I need the image in NSData being the original RAW image with no modifications.
You should look into the getBytes method of ALAssetRepresentation.
This gives you the original RAW image data of your image and also makes it possible to use a buffer to process the image instead of reading the image into memory all at once.
And of course you can always generate NSData from the getBytes method.
Cheers,
Hendrik
If you already have your ALAsset, you should be able to get an NSData of the default representation using the following:
NSData *data = [NSData dataWithContentsOfURL:[[asset defaultRepresentation] url]];
Related
I use libHary to create PDF.
I use this answer iOS SDK - Programmatically generate a PDF file to create pdf.
In this library method HPDF_LoadPngImageFromFile exist, but I need to load image from data (or UIImage). How can I do that?
Now the best solution for me is to right data to png file and then load it, but I thing better solution should exist.
LibHaru is platform independent so it does not know about about UIImage or NSData.
You have 2 options:
1. Save the UIImage/NSData to a file and then load the image from the file using HPDF_LoadPngImageFromFile method or
2. Save the UIImage to a NSData object, get a pointer to the NSData buffer ([nsdataobject bytes] method) and then use HPDF_LoadPngImageFromMem to load the image from memory.
I'm try to allow users to pull images out of their Photos collections using ALAssetsLibrary. Users can then upload these images. My goal is to allow users to upload any GIFs they may have in their library w/o loosing any animation they may have.
For PNG and JPEG files I can grab the ALAssetRepresentation, use - (CGImageRef)fullResolutionImage to get a CGImageRef, and then save it to NSData using UIImageJPEGRepresentation or UIImagePNGRepresentation.
However, because no similar function exists for GIF files, all I can do is covert the GIF to either JPEG or PNG, but then I lose the animation.
Is there either
a way to grab the NSData straight from an ALAssetRepresentation object or
a way to go from ALAssetRepresentation -> CGImageRef -> NSData without loosing any gif animation frames?
Thanks in advance!
Yes, there is a quite simple way:
Use the getBytes:fromOffset:length:error: method of ALAssetRepresentation. This gives youthe raw file data of the ALAsset, in your case the GIF file.
I'm working on an iPhone App that uses the camera to take pictures, then I'm saving them to the Applications Documents directory. I'm using the following code to convert the UIImage to NSData,
NSData *imageData = [NSData dataWithData:UIImagePNGRepresentation(image)];
Then I write the NSData using
[imageData writeToFile:path atomically:NO]
It all works. The problem is that UIImagePNGRepresentation() is really slow. It takes 8-9 secs on my 3G to convert the image to NSData. This seems wrong to me. Does anyone have any experience with this? Is this just slow function or am I doing something terribly wrong?
Thanks
Are you sure you want to save pictures captured with the camera as PNG?
JPEG is a more appropriate format for photographs. Additionally, its likely much faster!
I'm trying to post an image to TwitPic.com using their API.
However, I have never posted an image using HTTPPOST or however else before.
Anybody enlighten me to how I can post NSData from a UIImage using their api?
TwitPic is expecting a multi-part form data. There is a great open source library called ASIHTTPRequest.
You can use their APIs and post your image as multi-part/form-data.
See below for the sample.
http://allseeing-i.com/ASIHTTPRequest/How-to-use
Use the UIImagePNGRepresentation function or its JPEG equivalent to turn a UIImage into an NSData:
http://developer.apple.com/iphone/library/documentation/UIKit/Reference/UIKitFunctionReference/Reference/reference.html#//apple_ref/c/func/UIImagePNGRepresentation
#Jamie:
Try:
[request setData:twitpicImage forKey:#"media"];
If the image view is actually displaying an image that is stored in a file on disk, use:
[request setFile:theImagePath forKey:#"media"];
This way, ASIHTTPRequest will stream the image data from disk, so you don't have to keep an NSData instance in memory.
Ta
Ben
Instead of setPostValue for the image, use setData instead.
I have an application which uploads file from iPhone to web server.
Problem is that I want to give users a control like from which they can select the file / photo from the device and which is than uploaded on server.
Can anyone help me
You can get the UIImage content as a JPEG or PNG wrapped in NSData:
NSData *data = UIImageJPEGRepresentation(image, 1);
if( data ) { // it's possible nil may be returned
;// do stuff here.
// see: link to other answer on SO below.
// if you want to write to file, try:
[data writeToFile:filePath atomically:YES];
}
File Upload to HTTP server in iphone programming
I think you want to use an ImagePickerController that is the system component to allow a user to choose a photo.