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Merge two pictures

Objective-C defines a small but powerful set of extensions to the ANSI C programming language that enables sophisticated object-oriented programming. Objective-C is the native language for Cocoa programming�it�s the language that the frameworks are written in, and the language that most applications are written in. You can also use some other languages�such as Python and Ruby�to develop programs using the Cocoa frameworks. It�s useful, though, to have at least a basic understanding of Objective-C because Apple�s documentation and code samples are typically written in terms of this language.

Sometimes you might need to merge two pictures into one to show on your iPhone or iPad app. There are many ways to accomplish this task and I would like to discuss one of the ways we are using here at Walden Systems, because we believe this is the most straightforward method to resize any given image.

Strategy to merge two pictures is fairly simple: First, we need to determine what final destination the picture you want to merge will be. Second, we need to create a rectangle for that size. Third, create an empty image object based on your new size. Fourth, superimpose your existing images onto your new image object.

Here are actual code samples:

The first thing you need to do is to set the size of the new image, to do so, use the following line:

     UIGraphicsBeginImageContext ( SOME_WIDTH, SOME_HEIGHT )

Then you add the first and second pictures giving them starting x and y coordinates and width and height.

     [YOUR_PICTURE_ONE_PTR drawInRect:CGRectMake( START_X, START_Y, SOME_WIDTH, SOME_HEIGHT)];
     [YOUR_PICTURE_TWO_PTR drawInRect:CGRectMake( START_X, START_Y, SOME_WIDTH, SOME_HEIGHT)];

Then you will need to set a new image to an UIImage object

     UIImage *NEW_DESTINATION_IMAGE = UIGraphicsGetImageFromCurrentImageContext();

Finally,

   UIGraphicsEndImageContext()

So, this is how a final code for merging two pictures will look like:

 1    - (UIImage )mergeImage:(UIImage )pic1 : (UIImage *) pic2 
 2    {
 3        // both images are the same size so we can use the width of any image
 4        float     width = pic1.size.width;
 5        // both images are the same size so we can double the height of any image
 6        float     height = pic1.size.height * 2 ;
 7        UIGraphicsBeginImageContext(width, height);
 8     
 9        [pic1 drawInRect:CGRectMake(0, 0, pic1.size.width, pic1.size.height)];
10        //  note the starting Y coordinate is the height of pic1
11        [pic2 drawInRect:CGRectMake(0, pic1.size.height, pic2.size.width, pic2.size.height)];
12        UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();    
13        UIGraphicsEndImageContext();
14        return newImage;
15    }