How to write text on image in Objective-C (iOS)?

Question

I want to make an image like this programmatically:

I have the upper image and text with me. Should I write text on the image?

I want to make it a complete .png image(image + label) and set it as the background of the button.

Answer 1

Here is the Swift version.

func textToImage(drawText: NSString, inImage: UIImage, atPoint:CGPoint)->UIImage{

    // Setup the font specific variables
    var textColor: UIColor = UIColor.whiteColor()
    var textFont: UIFont = UIFont(name: "Helvetica Bold", size: 12)!

    //Setup the image context using the passed image.
    UIGraphicsBeginImageContext(inImage.size)

    //Setups up the font attributes that will be later used to dictate how the text should be drawn
    let textFontAttributes = [
        NSFontAttributeName: textFont,
        NSForegroundColorAttributeName: textColor,
    ]

    //Put the image into a rectangle as large as the original image.
    inImage.drawInRect(CGRectMake(0, 0, inImage.size.width, inImage.size.height))

    // Creating a point within the space that is as bit as the image.
    var rect: CGRect = CGRectMake(atPoint.x, atPoint.y, inImage.size.width, inImage.size.height)

    //Now Draw the text into an image.
    drawText.drawInRect(rect, withAttributes: textFontAttributes)

    // Create a new image out of the images we have created
    var newImage: UIImage = UIGraphicsGetImageFromCurrentImageContext()

    // End the context now that we have the image we need
    UIGraphicsEndImageContext()

    //And pass it back up to the caller.
    return newImage

}

To call it you just pass in an image.

textToImage("000", inImage: UIImage(named:"thisImage.png")!, atPoint: CGPointMake(20, 20))

The following links helped me get this straight.

Swift - Drawing text with drawInRect:withAttributes:

How to write text on image in Objective-C (iOS)?

The original goal was to create a dynamic image that I could use in an AnnotaionView such as putting a price at a given location on a map and this worked out great for it. Hope this helps someone trying to do the same thing.

Answer 2

Swift 3

extension UIImage {

    func textToImage(drawText: NSString, atPoint:CGPoint) -> UIImage? {

        // Setup the font specific variables
        let textColor: UIColor = UIColor.white
        let textFont: UIFont = UIFont(name: "Helvetica Bold", size: 12)!

        //Setup the image context using the passed image.
        UIGraphicsBeginImageContext(self.size)

        //Setups up the font attributes that will be later used to dictate how the text should be drawn
        let textFontAttributes = [
            NSFontAttributeName: textFont,
            NSForegroundColorAttributeName: textColor,
            ] as [String : Any]

        //Put the image into a rectangle as large as the original image.
        self.draw(in: CGRect(x:0, y:0, width:self.size.width, height: self.size.height))

        // Creating a point within the space that is as bit as the image.
        let rect: CGRect = CGRect(x:atPoint.x, y:atPoint.y, width:self.size.width, height:self.size.height)

        //Now Draw the text into an image.
        drawText.draw(in: rect, withAttributes: textFontAttributes)

        // Create a new image out of the images we have created
        let newImage: UIImage? = UIGraphicsGetImageFromCurrentImageContext()

        // End the context now that we have the image we need
        UIGraphicsEndImageContext()

        //And pass it back up to the caller.
        return newImage

    }
}

Answer 3

My function can add text water mark on image with 45 degree and 90 degree rotations

+(UIImage *)drawText:(NSString *)text diagonallyOnImage:(UIImage *)image rotation:(WatermarkRotation)rotation{

    UIColor *textColor = [UIColor colorWithRed:255 green:0 blue:0 alpha:0.2];//[UIColor colorWithWhite:0.5 alpha:1.0];
    UIFont *font = [UIFont systemFontOfSize:250];

    // Compute rect to draw the text inside
    NSDictionary *attr = @{NSForegroundColorAttributeName: textColor, NSFontAttributeName: font};
    CGSize textSize = [text sizeWithAttributes:attr];
    CGSize imageSize = image.size;
    // Create a bitmap context into which the text will be rendered.
    UIGraphicsBeginImageContext(textSize);
    // Render the text
    [text drawAtPoint:CGPointMake(0,0) withAttributes:attr];
    // Retrieve the image
    UIImage* img = UIGraphicsGetImageFromCurrentImageContext();

    CGImageRef imageRef = [img CGImage];
    CGBitmapInfo bitmapInfo = CGImageGetBitmapInfo(imageRef);
    CGColorSpaceRef colorSpaceInfo = CGImageGetColorSpace(imageRef);


    CGContextRef bitmap = CGBitmapContextCreate(NULL, textSize.width, textSize.width, CGImageGetBitsPerComponent(imageRef), CGImageGetBytesPerRow(imageRef), colorSpaceInfo, bitmapInfo);

    switch (rotation) {
        case WatermarkRotation90left:
            CGContextRotateCTM (bitmap, DEGREES_RADIANS(-90));
            CGContextTranslateCTM(bitmap, -textSize.width, 0);
            break;

        case WatermarkRotation90right:
            CGContextRotateCTM (bitmap, DEGREES_RADIANS(90));
            CGContextTranslateCTM(bitmap, 0, -textSize.width);
            break;

        case WatermarkRotation45ltr:
            CGContextRotateCTM (bitmap, DEGREES_RADIANS(45));
            CGContextTranslateCTM(bitmap, textSize.width/4, -textSize.width/2);
            break;

        case WatermarkRotation45rtl:
            CGContextRotateCTM (bitmap, DEGREES_RADIANS(-45));
            CGContextTranslateCTM(bitmap, -textSize.width/2, textSize.width/4);
            break;

        default:
            break;
    }

    CGContextDrawImage(bitmap, CGRectMake(0, (textSize.width/2)-(textSize.height/2), textSize.width, textSize.height), imageRef);
    CGImageRef ref = CGBitmapContextCreateImage(bitmap);
    UIImage* newImage = [UIImage imageWithCGImage:ref];

    UIGraphicsBeginImageContext( imageSize );

    // Use existing opacity as is
    [image drawInRect:CGRectMake(0,0,imageSize.width,imageSize.height)];


    if (rotation == WatermarkRotation90left) {
        [newImage drawInRect:CGRectMake(-((textSize.width/2)-(textSize.height/2)),(imageSize.height/2)-(textSize.width/2),textSize.width,textSize.width) blendMode:kCGBlendModeNormal alpha:1.0];
    }else if(rotation == WatermarkRotation90right){
        [newImage drawInRect:CGRectMake((imageSize.width-textSize.width/2)-(textSize.height/2),(imageSize.height/2)-(textSize.width/2),textSize.width,textSize.width) blendMode:kCGBlendModeNormal alpha:1.0];
    }else{
        [newImage drawInRect:CGRectMake((imageSize.width/2)-(textSize.width/2),(imageSize.height/2)-(textSize.width/2),textSize.width,textSize.width) blendMode:kCGBlendModeNormal alpha:1.0];
    }


    UIImage *mergedImage = UIGraphicsGetImageFromCurrentImageContext();


    UIGraphicsEndImageContext();
    return mergedImage;
}

Enum for rotation:

typedef enum:NSUInteger{
    WatermarkRotation90left=1,
    WatermarkRotation90right,
    WatermarkRotation45ltr,
    WatermarkRotation45rtl
}WatermarkRotation;

Note: Use 0 for drawing watermark in centre of image.(Default case of switch statement)

Add this macro for degree to radian:

#define DEGREES_RADIANS(angle) ((angle) / 180.0 * M_PI)

Hope this helps !!!

Answer 4

UIImageView *imageView = [UIImageView alloc];
imageView.image = [UIImage imageNamed:@"img.png"];
UILabel *label = [UILabel alloc];
label.text = @"Your text";
[imageView addsubview:label];

Set the frame of the label where you want the label to be displayed.

Answer 5

Draw text inside an image and return the resulting image:

+(UIImage*) drawText:(NSString*) text 
             inImage:(UIImage*)  image 
             atPoint:(CGPoint)   point 
{

    UIFont *font = [UIFont boldSystemFontOfSize:12];
    UIGraphicsBeginImageContext(image.size);
    [image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
    CGRect rect = CGRectMake(point.x, point.y, image.size.width, image.size.height);
    [[UIColor whiteColor] set];
    [text drawInRect:CGRectIntegral(rect) withFont:font]; 
    UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    return newImage;
}

Usage:

// note: replace "ImageUtils" with the class where you pasted the method above
UIImage *img = [ImageUtils drawText:@"Some text"
                            inImage:img 
                            atPoint:CGPointMake(0, 0)];

Change the origin of the text inside the image from 0,0 to whatever point you like.

To paint a rectangle of solid color behind the text, add the following before the line [[UIColor whiteColor] set];:

[[UIColor brownColor] set];
CGContextFillRect(UIGraphicsGetCurrentContext(), 
                  CGRectMake(0, (image.size.height-[text sizeWithFont:font].height), 
                                  image.size.width, image.size.height));

I'm using the text size to calculate the origin for the solid color rectangle, but you can replace it with any number.

Answer 6

Here is a Swift version which correctly centers the text on the image. This works with text of various sizes.

func addTextToImage(text: NSString, inImage: UIImage, atPoint:CGPoint)     -> UIImage{

    // Setup the font specific variables
    let textColor = YOURCOLOR
    let textFont = YOUR SIZE

    //Setups up the font attributes that will be later used to dictate how the text should be drawn
    let textFontAttributes = [
        NSFontAttributeName: textFont,
        NSForegroundColorAttributeName: textColor,
    ]

    // Create bitmap based graphics context
    UIGraphicsBeginImageContextWithOptions(inImage.size, false, 0.0)

    //Put the image into a rectangle as large as the original image.
    inImage.drawInRect(CGRectMake(0, 0, inImage.size.width, inImage.size.height))

    // Our drawing bounds
    let drawingBounds = CGRectMake(0.0, 0.0, inImage.size.width, inImage.size.height)

    let textSize = text.sizeWithAttributes([NSFontAttributeName:textFont])
    let textRect = CGRectMake(drawingBounds.size.width/2 - textSize.width/2, drawingBounds.size.height/2 - textSize.height/2,
        textSize.width, textSize.height)

    text.drawInRect(textRect, withAttributes: textFontAttributes)

    // Get the image from the graphics context
    let newImag = UIGraphicsGetImageFromCurrentImageContext()
    UIGraphicsEndImageContext()

    return newImag

}