I m new to IPhone Application development.
Actually, I converted UIImage to BASE64 String and sent to server side. It was about 58000 character length.
They, stored as Blob,now it is 5 to 6 character length. They are giving this 5 charecter blob data.
So, How can i reconstructed this blob to string ,which i sent?
Please reply.
Have you tried this:
NSData *cont=[[NSData alloc]initWithBytes:[blob_data bytes] length:[blob_data length]];
and then convert data into NSString using NSString initWithData.
I will suggest you to do encryption AES 128 and after that compression gzip in order to reduce the bandwidth wastage. Also it also make your data secure.At the server side do this in reverse order you will get origional plain data.
Related
I have seen this thread, and the encryption techniques mentioned there is working well. But not in all cases.
Requirement:
Simple, take one image, encrypt it, and store the encrypted data. Later, get the encrypted data, decrypt it, recreate the original image and show.
What I have done
From the above mentioned thread, I found NSData additions for AES 256 encryption. I tried to use it but with partial success. This is the code
//encryption
NSData *srcData = UIImageJPEGRepresentation(srcImage, 1.0);
NSLog(#"srcData length : %d",[srcData length]);
NSData *encryptedData = [srcData AES256EncryptWithKey:KEY];
NSLog(#"encrypted data length : %d",[encryptedData length]);
........
//later..
//decryption
decryptedImage = [UIImage imageWithData:[encryptedData AES256DecryptWithKey:KEY]];
imageView.image = decryptedImage;
What is happening
For a small image, say image with resolution 48*48, this code is working successfully. But when I run the code in an image with higher resolutions, say 256 * 256, the method AES256EncryptWithKey failing with error kCCBufferTooSmall (-4301).
Questions
Does AES 256 impose any limit on the size (in bytes) of the payload
to be encrypted?
If the answer to first question is YES, then what kind of
encryption algorithm to use in iphone, to encrypt image (probably
big ones)?
If the answer to the first question is NO, then why this error?
No, not really. Some hash functions do have a maximum, but that's more in the order of 2^64, so generally you don't have to worry.
N/A
It has probably something to do with the dataWithBytesNoCopy in combination with the malloc call, but it is hard to find out without actually running the code.
Note that that wrapper is pretty braindead, as it does require encrypting all at once, without using CCCryptorUpdate. It does not use an IV which jeopardizes security. It handles the keys as strings. Finally, it creates too big a buffer size for decryption. You are better off creating your own using a more reliable source.
I'm allowing the users of my app to either take a pic or select one from their library. When selected I need to get the images' data and convert it to a string so I can send it to a web service.
The problem I'm currently having is that [NSString initWithData:] is returning nil when I have the encoding set to UTF8. I need to set it to UTF8 for the XML message.
NSString *dataString = [[NSString alloc] initWithData:UIImageJPEGRepresentation(theImage, 1.0) encoding:NSUTF8StringEncoding];
Thanks for any advice!
You can't convert an UIImage to NSString by using initWithData:encoding: method. This method is only for converting an string's data to NSString (an Text File for example).
If you are trying to convert any kind of binary data to NSString, there are some kind of encoding available. Base64 is widely used. Also your server should have the ability to decode what you've sent.
In addition, in most cases, send an image to server just need to POST it in binary as it used to be.
I am converting image to NSdata using UIImageJPEGRepresentation(image, 1.0) and then encoding it to base64 using base64 helper class
NSString *imageOne = [self encodeBase64WithData:[imageDict objectForKey:#"ImageOne"]];
and finally sending it to server using post method as json parameter and in server side using php method to decode it.
/* encode & write data (binary) */
$ifp = fopen($imageNameWithPath, "wb" );
fwrite($ifp, base64_decode($base64ImageString));
fclose($ifp);
After decoding it, I am saving the file as jpeg image and the file is created with proper size and extension but problem is that when I open it, I get the DIMENSION OF IMAGE as 0X0 ..(problem is here)
Server side script is correct as our android developer is also sending base64string and the image is saved as jpeg with proper size and dimension.
This problem is only from iphone side when sending to server for decoding. I have decoded the image using my base64 helper class and it works fine on my iPhone device.
UIImageView *viewImage = [[UIImageView alloc] initWithImage:[UIImage imageWithData: [self decodeBase64WithString:[registerDataDict objectForKey:#"imageOne"]]]];
[self.view addSubview:viewImage];
Is the process followed by me correct on the device or do I need to change something? Help would be appreciated.
There are variants on the extra chars used to get to the 65 needed for base64 encoding (26 uppercase + 26 lowercase + 10 digits = 62), and different encoders may use a different subset. PHP is expecting them to be ['+', '/', '='], your application may be using something like ['-', '_', '='].
Once you figure out what the mapping is you can use str_replace before the decode in php.
See the wikipedia page on base64 or the php documentation for base64_decode for more info.
I'm successfully using this with several OAuth providers: Base64Transcoder.c It's a C class, you can easily turn it into a Objective-C class if you like.
I'm encoding like this:
char base64Result[32];
size_t theResultLength = 32;
[Base64Transcoder base64EncodeData:digest digestLength:CC_SHA1_DIGEST_LENGTH base64Result:base64Result resultLength:&theResultLength];
NSData *theData = [NSData dataWithBytes:base64Result length:theResultLength];
NSString *base64EncodedResult = [[NSString alloc] initWithData:theData encoding:NSUTF8StringEncoding];
Hmm well, I turned the C function base64EncodeData of the original class into an Objective-C method but you get the idea.
I have some image data (jpeg) I want to send from my iPhone app to my webservice. In order to do this, I'm using the NSData from the image and converting it into a string which will be placed in my JSON.
Currently, I'm doing this:
NSString *secondString = [[NSString alloc] initWithBytes:[result bytes]
length:[result length]
encoding:NSUTF8StringEncoding];
Where result is of type NSData. However, secondString appears to be null even though result length returns a real value (like 14189). I used this method since result is raw data and not null-terminated.
Am I doing something wrong? I've used this code in other areas and it seems to work fine (but those areas I'm currently using it involve text not image data).
TIA.
For binary data, better to encode it using Base64 encoding then decode it in you webservice. I use NSData+Base64 class downloaded from here, this reference was also taken from Stackoverflow, an answer made by #Ken (Thanks Ken!).
You are not converting the data to a string. You are attempting to interpret it as a UTF-8 encoded string, which will fail unless the data really is a UTF-8 encoded string. Your best bet is to encode it somehow, perhaps with Base64 as Manny suggests, and then decode it again on the server.
I am aware this question has been asked several times, but I was unable to find a definate answer that would best fit my situation.
I want the ability to have the user select an image from the library, and then that image is converted to an NSData type. I then have a requirement to call a .NET C# webservice via a HTTP get so ideally I need the resulting string to be UTF8 encoded.
This is what I have so far:
NSData *dataObj = UIImageJPEGRepresentation(selectedImage, 1.0);
[picker dismissModalViewControllerAnimated:YES];
NSString *content = [[NSString alloc] initWithData:dataObj encoding:NSUTF8StringEncoding];
NSLog(#"%#", content);
The NSLog statement simply produces output as:
2009-11-29 14:13:33.937 TestUpload2[5735:207] (null)
Obviously this isnt what I hoped to achieve, so any help would be great.
Kind Regards
You can't create a UTF-8 encoded string out of just any arbitrary binary data - the data needs to actually be UTF-8 encoded, and the data for your JPEG image obviously is not. Your binary data doesn't represent a string, so you can't directly create a string from it - -[NSString initWithData:encoding:] fails appropriately in your case.
Assuming you're using NSURLConnection (although a similar statement should be true for other methods), you'll construct your NSMutableURLRequest and use -setHTTPBody: which you need to pass an NSData object to. I don't understand why you would be using a GET method here since it sounds like you're going to be uploading this image data to your web service - you should be using POST.