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.
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 am making a small application where I am receiving images from web-service. I am getting the image url. And the format of images is different different like .jpg,.gif,.png etc. And I want to save these images into my sandbox and later on show it into image view.
To do this I am giving a self name and gave the extension to .png. But at the time of retrieving the .png images are shown but different one's are not shown. So can you give me any idea how to convert all images to .png format or any other approach to do this?
after you retrieve your images/url save them this way:
NSData *imageData = UIImagePNGRepresentation(image);
[imageData writeToFile:savedImagePath atomically:YES];
Would it not be easier if you use an image library like SDWebImage which handles all the asynchronous image downloading and caching of the image onto your device?
https://github.com/rs/SDWebImage
Then you can do something like:
[myImageView setImageWithURL:[NSURL URLWithString:#"http://www.domain.com/path/to/image.jpg"]
placeholderImage:[UIImage imageNamed:#"placeholder.png"]];
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]];
What's the best way to save and retrieve an array of images across app restarts?
I'm implementing a caching feature for offline viewing of downloaded images and just want to make sure I'm using the right persisting methods.
Thanks!
The quickest & probably best solution would be to persist your images to disk, no question about it.
You could do something like this to save them as JPEG.
NSData *data = UIImageJPEGRepresentation(image, 1.0f);
[data writeToFile:imagePath atomically:YES];
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:.