Go from image url rep from asset library to base64 - ios

Question

I am ultimately trying to convert an array of photos that are in a dictionary in url rep form to base64 to be sent over json.
Here is the dictionary code and log of it:
NSDictionary *dict = [self.form dictionaryWithValuesForKeys:keys];
NSLog(#"dict::%#",dict);
NSLog:
dict::{
boardLodgingFurnished = "<null>";
caption = "<null>";
cars = "";
photos = (
{
caption = "";
urlRep = "assets-library://asset/asset.JPG?id=CE8A426B-3B59-4172-8761-CC477F3BB3EE&ext=JPG";
},
{
caption = "";
urlRep = "assets-library://asset/asset.JPG?id=F4B68A42-1CA0-4880-9FB5-177CB091A28C&ext=JPG";
}
);
yearsAtLocation = "";
yearsInTheBusiness = "";
}
So for each photo in the dictionary I would like to take the urlRep and convert that to a base64 string and replace the urlRep with it in the dictionary.
What I have right now..not sure if I am going in the right direction:
for (id imageURL in [dict objectForKey:#"photos"])
{
ALAssetsLibrary *library = [ALAssetsLibrary new];
ALAsset *ourAsset = [self assetForURL:imageURL withLibrary:library];
/* Check out ALAssets */
NSLog(#"%#", ourAsset);
ALAssetRepresentation *representation = [ourAsset defaultRepresentation];
CGImageRef imageRef = [representation fullResolutionImage];
//TODO: Deal with JPG or PNG
NSData *imageData = UIImageJPEGRepresentation([UIImage imageWithCGImage:imageRef], 0.1);
NSLog(#"imagedata??%#", [imageData base64EncodedString]);
//need to know how to add this back to dict
}
the below method is called from above but crashes on the while loop with
-[__NSDictionaryI scheme]: unrecognized selector sent to instance 0x166dd090
2014-01-03 10:57:27.361 Inspection App[2728:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI scheme]: unrecognized selector sent to instance 0x166dd090'
method
- (ALAsset *)assetForURL:(NSURL *)url withLibrary:(ALAssetsLibrary *)assetsLibrary {
__block ALAsset *result = nil;
__block NSError *assetError = nil;
dispatch_semaphore_t sema = dispatch_semaphore_create(0);
[assetsLibrary assetForURL:url resultBlock:^(ALAsset *asset) {
result = asset;
dispatch_semaphore_signal(sema);
} failureBlock:^(NSError *error) {
assetError = error;
dispatch_semaphore_signal(sema);
}];
if ([NSThread isMainThread]) {
while (!result && !assetError) {
[[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode beforeDate:[NSDate distantFuture]];
}
}
else {
dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
}
return result;
}
edit:
if (photoUrls.count) {
for (id photos in photoUrls){
NSString *urlString = photos;
[self base64ImageAtUrlString:urlString result:^(NSString *base64) {
NSLog(#"imagedata??%#", base64);
}];
}
}
else {
NSLog(#"where are my urls?");
}
NSMutableDictionary *jsonWithPhotos = [dict mutableCopy];
[jsonWithPhotos setObject:convertedImages forKey:#"photo64"];
NSLog(#"jjson photos::%#", jsonWithPhotos);
updated method
- (void)base64ImageAtUrlString:(NSString *)urlString result:(void (^)(NSString *))completion {
NSURL *url = [NSURL URLWithString:urlString];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library assetForURL:url resultBlock:^(ALAsset *asset) {
// borrowing your code, here... didn't check it....
ALAssetRepresentation *representation = [asset defaultRepresentation];
CGImageRef imageRef = [representation fullResolutionImage];
//TODO: Deal with JPG or PNG
NSData *imageData = UIImageJPEGRepresentation([UIImage imageWithCGImage:imageRef], 0.1);
NSString *base64 = [imageData base64EncodedString];
completion(base64);
[convertedImages addObject:base64];
// NSLog(#"converted::%#",convertedImages);
} failureBlock:^(NSError *error) {
NSLog(#"that didn't work %#", error);
}];
}
When i log jsonWithPhotos the object photo64 is just a blank array

Answer 1

The crash is due to a false assumption in the code about the dictionary. Given the posted description of the dictionary parsed as json, you'd need to get the urls like this:
// collect the photo urls in an array
NSMutableArray *photoUrls = [NSMutableArray array];
// photos is an array of dictionaries in the dictionary
NSArray *photos = dict[#"photos"];
for (NSDictionary *photo in photos) {
// photo is a dictionary containing a "caption" and a "urlRep"
[photoUrls addObject:photo[#"urlRep"]];
}
Now you can proceed with a method whose job is just the conversion. Your question might contain a lot more questions about how to do this. I'd recommend starting simple. See if you can do one conversion. Test it by writing the reverse, from base64 back to an image.
Edit 0: Without deeply checking it, I'd restructure your encoding attempt to look like this:
- (void)base64ImageAtUrlString:(NSString *)urlString result:(void (^)(NSString *))completion {
NSURL *url = [NSURL URLWithString:urlString];
ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
[library assetForURL:url resultBlock:^(ALAsset *asset) {
// borrowing your code, here... didn't check it....
ALAssetRepresentation *representation = [asset defaultRepresentation];
CGImageRef imageRef = [representation fullResolutionImage];
//TODO: Deal with JPG or PNG
NSData *imageData = UIImageJPEGRepresentation([UIImage imageWithCGImage:imageRef], 0.1);
NSString *base64 = [imageData base64EncodedString];
completion(base64);
} failureBlock:^(NSError *error) {
NSLog(#"that didn't work %#", error);
}];
}
Call it like this:
if (photoUrls.count) {
NSString *urlString = photoUrls[0];
[self base64ImageAtUrlString:urlString result:^(NSString *base64) {
NSLog(#"imagedata??%#", base64);
}];
} else {
NSLog(#"where are my urls?");
}
Once it's working, see if you can reverse it, making an image out of the base64 data. Finally, once all that's working, you can deal with potential memory issues. My advice there is to consider encoding one at a time, post one at a time to the server and release everything in between.
Edit 1 - Per followup question, if you want to replace all of the urls in the url array with base64 encodings, it might go something like this (remember that this might use a lot of memory):
- (void)base64ImagesAtUrls:(NSMutableArray *)urls result:(void (^)(void))completion {
__block NSInteger completed = 0; // this is how we'll know that we're done
// this approach doesn't depend on the asset library retrievals completing
// sequentially, even though they probably will
for (int i=0; i<urls.count; i++) {
NSString *urlString = urls[i];
[self base64ImageAtUrlString:urlString result:^(NSString *base64) {
[urls replaceObjectAtIndex:i withObject:base64];
if (++completed == urls.count) completion();
}];
}
}