Converting image to NSData & back is nil

Question

When I do

UIImage *photo = [UIImage imageNamed:@"sample_thumbnail.png"];
self.thumbnail.image = photo;

I see the thumbnail, which is a PNG, fine. When I convert to NSData & back by doing:

UIImage *photo = [UIImage imageNamed:@"sample_thumbnail.png"];
NSData *data = UIImagePNGRepresentation(photo);
self.photoData = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
self.thumbnail.image = [UIImage imageWithData:[self.photoData dataUsingEncoding:NSUTF8StringEncoding]];

self.photoData is nil.

Why is this happening?

Answer 1

I think the problem is with the way you create your image back from NSData instance. Give it a try to this one instead:

UIImage *photo = [UIImage imageNamed:@"sample_thumbnail.png"];
NSData *data = UIImagePNGRepresentation(photo);
UIImage *image = [UIImage imageWithData:data];

__UPDATE__

below is an excerpt from this post

- (NSString *)imageToNSString:(UIImage *)image
{
    NSData *imageData = UIImagePNGRepresentation(image);

    return [imageData base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
}

- (UIImage *)stringToUIImage:(NSString *)string
{
    NSData *data = [[NSData alloc]initWithBase64EncodedString:string
                                                  options:NSDataBase64DecodingIgnoreUnknownCharacters];

    return [UIImage imageWithData:data];
}