[iOS] QRコードを生成して画像に合成する ref: http://qiita.com/bugcloud/items/3962d5ffdb883021f813

file1.txt

platform :ios
pod 'QR-Code-Encoder-for-Objective-C'

sample.mm

//the qrcode is square. now we make it 250 pixels wide
int qrcodeImageDimension = 250;

//the string can be very long
NSString* aVeryLongURL = @"http://thelongestlistofthelongeststuffatthelongestdomainnameatlonglast.com/";

//first encode the string into a matrix of bools,
//TRUE for black dot and FALSE for white. Let the encoder decide the error correction level and version
DataMatrix* qrMatrix = [QREncoder encodeWithECLevel:QR_ECLEVEL_AUTO version:QR_VERSION_AUTO string:aVeryLongURL];

//then render the matrix
UIImage* qrcodeImage = [QREncoder renderDataMatrix:qrMatrix imageDimension:qrcodeImageDimension];

SomeViewController.mm

#import "QREncoder.h"

...

#pragma mark -
#pragma UIImagePickerControllerDelegate

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info
{
    UIImage *image = [info valueForKey:UIImagePickerControllerOriginalImage];
    CGSize size = [image size];
    UIGraphicsBeginImageContext(size);
    CGRect rect;
    rect.origin = CGPointZero;
    rect.size = size;
    [image drawInRect:rect];

    //upload image and get its URL
    NSString *imageUrl = @"http://xxxxxxxxxx";
    DataMatrix *qrMatrix = [QREncoder encodeWithECLevel:QR_ECLEVEL_AUTO version:QR_VERSION_AUTO string:imageUrl];
    int qrDimention = 640;
    UIImage *qrImage = [QREncoder renderDataMatrix:qrMatrix imageDimension:qrDimention];
    //At first, draw white background and then draw QR code
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextSetFillColorWithColor(context, [UIColor whiteColor].CGColor);
    CGContextFillRect(context, CGRectMake(image.size.width - qrDimention - 140.0f,
                                          image.size.height - qrDimention - 140.0f,
                                          qrDimention + 80.0f,
                                          qrDimention + 80.0f));
    [qrImage drawAtPoint:CGPointMake(image.size.width - qrDimention - 100.0f,
                                     image.size.height - qrDimention - 100.0f)];

    UIImage *mergedImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    image = mergedImage;
    ALAssetsLibrary *library = [[ALAssetsLibrary alloc] init];
    [library writeImageToSavedPhotosAlbum:image.CGImage
                              orientation:(ALAssetOrientation)image.imageOrientation
                          completionBlock:^(NSURL *assetURL, NSError *error) {
        /* Do something */
    }];
}