How to right some text on an image(png) in iPhone objective-c?

Sanchit · July 2011

Hello Friends,

I am very new to the iPhone development and this site. I am working on a project where I have to write some text on a png image and after writing again save it as png. Is it possible through objective-c? Please provide me any sample code or any tutorial for it.

Waiting for replies.

Thanks in advance

dany_dev · July 2011

you can do something like that
Add text to image (UIImage)


//Add text to UIImage

-(UIImage *)addText:(UIImage *)img text:(NSString *)text1{

    int w = img.size.width;

    int h = img.size.height; 

    //lon = h - lon;

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();

    CGContextRef context = CGBitmapContextCreate(NULL, w, h, 8, 4 * w, colorSpace, kCGImageAlphaPremultipliedFirst);

    

    CGContextDrawImage(context, CGRectMake(0, 0, w, h), img.CGImage);

    CGContextSetRGBFillColor(context, 0.0, 0.0, 1.0, 1);

    char* text = (char *)[text1 cStringUsingEncoding:NSASCIIStringEncoding];// \"05/05/09\";

    CGContextSelectFont(context, \"Arial\", 18, kCGEncodingMacRoman);

    CGContextSetTextDrawingMode(context, kCGTextFill);

    CGContextSetRGBFillColor(context, 255, 255, 255, 1);

 

    //rotate text

    CGContextSetTextMatrix(context, CGAffineTransformMakeRotation( -M_PI/4 ));

    CGContextShowTextAtPoint(context, 4, 52, text, strlen(text));

    CGImageRef imageMasked = CGBitmapContextCreateImage(context);

    CGContextRelease(context);

    CGColorSpaceRelease(colorSpace);

    return [UIImage imageWithCGImage:imageMasked];

}

Sanchit · July 2011

Thanks dany_dev, You provide me the awesomest solution, for which I was looking. Is there any way to wrap the text according to the image size? If possible then please help me on it. Thanks again

dany_dev · July 2011

what you mean exactly? I don't understand, you want to make the text big so that fit the width of your UIImage?

Sanchit · July 2011

Actually My text is more than the width of the image. So, Can I wrap it according to the image width. (Only two lines)

dany_dev · July 2011

you can calculate the size of your text,

this is a cool method to calculate the width of your text with a fixed size
// do something here Blog Archive Balance


- (CGFloat)calculateTextWidth:(NSString *)text 
{ 
    CGSize fullSize = [UIScreen mainScreen].applicationFrame.size; 
    UIGraphicsBeginImageContext(fullSize);
    CGContextRef context = UIGraphicsGetCurrentContext();
 
    // calculate the text size
    CGContextSelectFont(context, [fontName UTF8String], fontSize, kCGEncodingMacRoman);
    CGContextSetTextMatrix(context, CGAffineTransformMakeScale(1.0, -1.0));
    CGContextSetTextDrawingMode(context, kCGTextInvisible);
 
    // measure the text
    CGPoint initialTextPosition = CGContextGetTextPosition(context);
    CGContextShowTextAtPoint(context, 0, 0, [text cStringUsingEncoding:NSASCIIStringEncoding], text.length);
    CGPoint finalTextPosition = CGContextGetTextPosition(context);
 
    UIGraphicsEndImageContext();  // !!!!!
 
    return finalTextPosition.x - initialTextPosition.x;
}

So now, just add fontSize as parameter to the method, and write a while loop to calculate the right maximum size to fix your width UIImage....

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