I am coding an iPhone application where images are transferred from one iPhone to another using Bluetooth. How do I archive an image and send it to another iPhone, then un-archive the image back? Archiving the image directly using NSKeyedarchiver doesn't work.
You can turn UIImage objects into NSData representations using the Image Manipulation function UIImageJPEGRepresentation or UIImagePNGRepresentation.
You can turn the NSData representation into a UIImage using the UIImage convenience method imageWithData: or initializer initWithData:.
Related
I'm writing a function to download a regular PNG file from web server and save it to iPhone Photos album. I don't get any error for my code listed below but UIImagePNGRepresentation doesn't perform the convert at all. All images I got were black. I have to enable "auto-enhanced" under Photos to display those image properly. Any clue what's wrong with my code? Thanks in advance.
UIImage *orgImg = [[UIImage alloc] initWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:#"http://server.com/test.png"]]];
NSData * convertedData = UIImagePNGRepresentation(orgImg);
UIImage * img = [UIImage imageWithData: convertedData];
// Save Image to Photo Album
UIImageWriteToSavedPhotosAlbum(img, self,
#selector(thisImage:hasBeenSavedInPhotoAlbumWithError:usingContextInfo:), nil);
Some more details of these two output images, orgImg and img:
If I pass orgImg to UIImageWriteToSavedPhotosAlbum directly, I did get the same PNG image hosted on the server. However Photos application on my iPhone displays it as a black image because Photos doesn't enhance PNG format automatically.
As for the img I got after using UIImagePNGRepresentation, the image data has been changed by the method, some meta data such as width/height have been removed from the original image. However Photos app on my iPhone still display it as an all black image.
Both images display properly if I copy them into either Safari or email. I didn't get any problem if I use JPEG in the server side either. Just curious why only PNG format doesn't work.
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]];
How does one load or fetch an image that was saved to disk?
I wrote the image to the documents filepath using NSData and a PNG representation. How does one get this image back? UIImage.
UIImage *theImage = [UIImage imageWithContentsOfFile:filePath];
As ever, see the UIImage documentation at Apple. It is your friend.
there are two normal ways to import images (from camera and from album) but I also want to take images of iphone phonebook, so what should I do ?
Below can be used for getting image from AddressBook
NSData *imgData = (NSData *)ABPersonCopyImageData(person);
UIImage *img = [UIImage imgaeWithData:imgData];
where person is of type ABRecordRef. Now as CFData and NSData are
toll-free bridged
, so you can simply type cast CFData to NSData and get the image
Here is the Tutorial
http://adeem.me/blog/2009/04/02/get-image-from-contact-stored-in-addressbook/
If with "phonebook" you mean AddressBook framework to access contacts data, try using Erica Sadun's AB cocoa wrapper. It includes a sample project, so it will be easy.
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.