Convert string of data to image - ios

Question

I have a jpg image which I am converting to data using the UIImageJPEGRepresentation function
I am then sending the data to a server online and getting it back when it is needed though I get this string:
<ffd8ffe0 00104a46 49460001 01000001 00010000 ffe10058 45786966 00004d4d...>
And I don't know how to convert it back to an image
Thanks in advance

Answer 1

I managed to find a way to do it by converting the string to a base64 string like this:
+ (NSString *) encodeToBase64:(NSData *) rawBytes {
return [StringMethods encodeToBase64:(const uint8_t*) rawBytes.bytes length:rawBytes.length];
}
+ (NSString *) encodeToBase64:(const uint8_t *)input length:(NSInteger) length {
NSMutableData *data = [NSMutableData dataWithLength:((length + 2) / 3) * 4];
uint8_t *output = (uint8_t *)data.mutableBytes;
for (NSInteger i = 0; i < length; i += 3) {
NSInteger value = 0;
for (NSInteger j = i; j < (i + 3); j++) {
value <<= 8;
if (j < length) {
value |= (0xFF & input[j]);
}
}
NSInteger index = (i / 3) * 4;
output[index + 0] = encodingTable[(value >> 18) & 0x3F];
output[index + 1] = encodingTable[(value >> 12) & 0x3F];
output[index + 2] = (i + 1) < length ? encodingTable[(value >> 6) & 0x3F] : '=';
output[index + 3] = (i + 2) < length ? encodingTable[(value >> 0) & 0x3F] : '=';
}
return [[NSString alloc] initWithData:data encoding:NSASCIIStringEncoding];
}
Then I saved it onto the server then when loading back in I used this function:
- (NSData *)base64DataFromString: (NSString *)string {
unsigned long ixtext, lentext;
unsigned char ch, inbuf[4], outbuf[3];
short i, ixinbuf;
Boolean flignore, flendtext = false;
const unsigned char *tempcstring;
NSMutableData *theData;
if (string == nil){
return [NSData data];
}
ixtext = 0;
tempcstring = (const unsigned char *)[string UTF8String];
lentext = [string length];
theData = [NSMutableData dataWithCapacity: lentext];
ixinbuf = 0;
while (true) {
if (ixtext >= lentext) {
break;
}
ch = tempcstring [ixtext++];
flignore = false;
if ((ch >= 'A') && (ch <= 'Z')) {
ch = ch - 'A';
} else if ((ch >= 'a') && (ch <= 'z')) {
ch = ch - 'a' + 26;
} else if ((ch >= '0') && (ch <= '9')) {
ch = ch - '0' + 52;
} else if (ch == '+') {
ch = 62;
} else if (ch == '=') {
flendtext = true;
} else if (ch == '/') {
ch = 63;
} else {
flignore = true;
}
if (!flignore) {
short ctcharsinbuf = 3;
Boolean flbreak = false;
if (flendtext) {
if (ixinbuf == 0) {
break;
}
if ((ixinbuf == 1) || (ixinbuf == 2)) {
ctcharsinbuf = 1;
} else {
ctcharsinbuf = 2;
}
ixinbuf = 3;
flbreak = true;
}
inbuf [ixinbuf++] = ch;
if (ixinbuf == 4) {
ixinbuf = 0;
outbuf[0] = (inbuf[0] << 2) | ((inbuf[1] & 0x30) >> 4);
outbuf[1] = ((inbuf[1] & 0x0F) << 4) | ((inbuf[2] & 0x3C) >> 2);
outbuf[2] = ((inbuf[2] & 0x03) << 6) | (inbuf[3] & 0x3F);
for (i = 0; i < ctcharsinbuf; i++) {
[theData appendBytes: &outbuf[i] length: 1];
}
}
if (flbreak) {
break;
}
}
}
return theData;
}
And finally to convert it into an image I was this simple method:
UIImage *image = [UIImage imageWithData:imageData];

Answer 2

Is what you are showing a string, or is that what you get when you display NSData? I believe that if you log binary data, it comes out as you've shown.
What you have shown is hexadecimal data, not base64, as the other poster suggested.
You could either write code that uses sscanf() to pull out int values from your hex string, or create an NSScanner object and use it's scanHexInt method. If you google "convert hex NSString to integer" you should find both approaches.
Since your values have spaces between them, NSScanner might be your best bet.

Answer 3

Issue
You are sending NSData to server not NSString, and that's why you are getting this NSData on that format read by you as NSString.
Solution
First you need to send it correctly as NSString to server by doing this:
NSData *imageData= UIImagePNGRepresentation(yourImage);
NSString *encodedString = [imageData base64EncodedStringWithOptions:0];
After you send it to NSString, now you get it back an manipulate it like this. I am using NSData Base64 library to perform this task.
You just manually copy these files to your project. Import the classes to your project and these lines to your code:
#import "NSData+Base64.h"
//This function converts your base64string (NSString Class) to NSData
NSData *data = [[NSData alloc] initWithData:[NSData dataFromBase64String:base64String]];
//Here is where you convert it to UIImage
UIImage *image = [UIImage imageWithData:data];
P.S You can also follow your answer, which to me seems correct, but I just wanted to let you know where were you doing wrong.

Answer 4

This seems to be a good answer for converting:
NSData *dataImage = [[NSData alloc] init];
dataImage = UIImagePNGRepresentation(image);
NSString *stringImage = [dataImage base64EncodedStringWithOptions:NSDataBase64Encoding64CharacterLineLength];
which you can find here:NSString to UIImage