How to retrieve the most recent photo from Camera Roll on iOS? - objective-c

Question

I'm having a hard figuring out how to programmatically retrieve the most recent photo in the camera roll without user intervention. To be clear, I do not want to use an Image Picker, I want the app to automatically grab the newest photo when the app opens.
I know this is possible because Ive seen a similar app do it, but I cant seem to find any info on it.

Answer 1

One way is to use AssetsLibrary and use n - 1 as the index for enumeration.
ALAssetsLibrary *assetsLibrary = [[ALAssetsLibrary alloc] init];
[assetsLibrary enumerateGroupsWithTypes:ALAssetsGroupSavedPhotos
usingBlock:^(ALAssetsGroup *group, BOOL *stop) {
if (nil != group) {
// be sure to filter the group so you only get photos
[group setAssetsFilter:[ALAssetsFilter allPhotos]];
if (group.numberOfAssets > 0) {
[group enumerateAssetsAtIndexes:[NSIndexSet indexSetWithIndex:group.numberOfAssets - 1]
options:0
usingBlock:^(ALAsset *result, NSUInteger index, BOOL *stop) {
if (nil != result) {
ALAssetRepresentation *repr = [result defaultRepresentation];
// this is the most recent saved photo
UIImage *img = [UIImage imageWithCGImage:[repr fullResolutionImage]];
// we only need the first (most recent) photo -- stop the enumeration
*stop = YES;
}
}];
}
}
*stop = NO;
} failureBlock:^(NSError *error) {
NSLog(#"error: %#", error);
}];

Answer 2

Instead of messing with the index, you can enumerate through the list in reverse. This pattern works well if you want the most recent image or if you want to list the images in a UICollectionView with the most recent image first.
Example to return the most recent image:
[group enumerateAssetsWithOptions:NSEnumerationReverse usingBlock:^(ALAsset *asset, NSUInteger index, BOOL *stop) {
if (asset) {
ALAssetRepresentation *repr = [asset defaultRepresentation];
UIImage *img = [UIImage imageWithCGImage:[repr fullResolutionImage]];
*stop = YES;
}
}];

Answer 3

In iOS 8, Apple added the Photos library which makes for easier querying. In iOS 9, ALAssetLibrary is deprecated.
Here's some Swift code to get the most recent photo taken with that framework.
import UIKit
import Photos
struct LastPhotoRetriever {
func queryLastPhoto(resizeTo size: CGSize?, queryCallback: (UIImage? -> Void)) {
let fetchOptions = PHFetchOptions()
fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
// fetchOptions.fetchLimit = 1 // This is available in iOS 9.
if let fetchResult = PHAsset.fetchAssetsWithMediaType(PHAssetMediaType.Image, options: fetchOptions) {
if let asset = fetchResult.firstObject as? PHAsset {
let manager = PHImageManager.defaultManager()
// If you already know how you want to resize,
// great, otherwise, use full-size.
let targetSize = size == nil ? CGSize(width: asset.pixelWidth, height: asset.pixelHeight) : size!
// I arbitrarily chose AspectFit here. AspectFill is
// also available.
manager.requestImageForAsset(asset,
targetSize: targetSize,
contentMode: .AspectFit,
options: nil,
resultHandler: { image, info in
queryCallback(image)
})
}
}
}
}

Answer 4

Swift 3.0:
1) Import Photos framework in your header before your class declaration.
import Photos
2) Add the following method, which returns the last image.
func queryLastPhoto(resizeTo size: CGSize?, queryCallback: #escaping ((UIImage?) -> Void)) {
let fetchOptions = PHFetchOptions()
fetchOptions.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]
let requestOptions = PHImageRequestOptions()
requestOptions.isSynchronous = true
let fetchResult = PHAsset.fetchAssets(with: PHAssetMediaType.image, options: fetchOptions)
if let asset = fetchResult.firstObject {
let manager = PHImageManager.default()
let targetSize = size == nil ? CGSize(width: asset.pixelWidth, height: asset.pixelHeight) : size!
manager.requestImage(for: asset,
targetSize: targetSize,
contentMode: .aspectFit,
options: requestOptions,
resultHandler: { image, info in
queryCallback(image)
})
}
}
3) Then call this method somewhere in your app (maybe a button action):
#IBAction func pressedLastPictureAttachmentButton(_ sender: Any) {
queryLastPhoto(resizeTo: nil){
image in
print(image)
}
}

Answer 5

To add to Art Gillespie's answer, using the fullResolutionImage uses the original image which — depending on the device's orientation when taking the photo — could leave you with an upside down, or -90° image.
To get the modified, but optimised image for this, use fullScreenImage instead....
UIImage *img = [UIImage imageWithCGImage:[repr fullScreenImage]];

Answer 6

Answer to the question (in Swift):
func pickingTheLastImageFromThePhotoLibrary() {
let assetsLibrary: ALAssetsLibrary = ALAssetsLibrary()
assetsLibrary.enumerateGroupsWithTypes(ALAssetsGroupSavedPhotos,
usingBlock: { (let group: ALAssetsGroup!, var stop: UnsafeMutablePointer<ObjCBool>) -> Void in
if (group != nil) {
// Be sure to filter the group so you only get photos
group.setAssetsFilter(ALAssetsFilter.allPhotos())
group.enumerateAssetsWithOptions(NSEnumerationOptions.Reverse,
usingBlock: { (let asset: ALAsset!,
let index: Int,
var stop: UnsafeMutablePointer<ObjCBool>)
-> Void in
if(asset != nil) {
/*
Returns a CGImage representation of the asset.
Using the fullResolutionImage uses the original image which — depending on the
device's orientation when taking the photo — could leave you with an upside down,
or -90° image. To get the modified, but optimised image for this, use
fullScreenImage instead.
*/
// let myCGImage: CGImage! = asset.defaultRepresentation().fullResolutionImage().takeUnretainedValue()
/*
Returns a CGImage of the representation that is appropriate for displaying full
screen.
*/
// let myCGImage: CGImage! = asset.defaultRepresentation().fullScreenImage().takeUnretainedValue()
/* Returns a thumbnail representation of the asset. */
let myCGImage: CGImage! = asset.thumbnail().takeUnretainedValue()
// Here we set the image included in the UIImageView
self.myUIImageView.image = UIImage(CGImage: myCGImage)
stop.memory = ObjCBool(true)
}
})
}
stop.memory = ObjCBool(false)
})
{ (let error: NSError!) -> Void in
println("A problem occurred: \(error.localizedDescription)")
}
}

Answer 7

Using Photos Library ( Objective-C )
PHFetchOptions *fetchOptions = [[PHFetchOptions alloc] init];
fetchOptions.sortDescriptors = #[[NSSortDescriptor sortDescriptorWithKey:#"creationDate" ascending:NO]];
PHFetchResult *assetsFetchResult = [PHAsset fetchAssetsInAssetCollection:assetCollection options:fetchOptions];
if (assetsFetchResult.count>0) {
PHAsset *asset = [assetsFetchResult objectAtIndex:0];
CGFloat scale = [UIScreen mainScreen].scale;
CGFloat dimension = 55.0f; // set your required size
CGSize size = CGSizeMake(dimension*scale, dimension*scale);
[[PHImageManager defaultManager] requestImageForAsset:asset
targetSize:size
contentMode:PHImageContentModeAspectFit
options:nil
resultHandler:^(UIImage *result, NSDictionary *info) {
// do your thing with the image
}
];
}