contentStretchTest.m

NSString *imageName = @"grid.png"; // the image is here: http://f.cl.ly/items/050w3k342y032F0E3n29/grid.png

UIImageView *imageView1 = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]] autorelease];
UIImageView *imageView2 = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]] autorelease];
UIImageView *imageView3 = [[[UIImageView alloc] initWithImage:[UIImage imageNamed:imageName]] autorelease];

CGSize imageSize;
imageSize.width = imageView1.frame.size.width;
imageSize.height = imageView1.frame.size.height;

CGSize stretchSize;
stretchSize.width = 50.0;
stretchSize.height = 100.0;

imageView1.contentStretch = CGRectMake(0.0, 0.0, stretchSize.width/imageSize.width, stretchSize.height/imageSize.height);
imageView2.contentStretch = imageView1.contentStretch;
imageView3.contentStretch = CGRectMake(100.0/imageSize.width, 100.0/imageSize.height, stretchSize.width/imageSize.width, stretchSize.height/imageSize.height);

// horizonzal stretch
imageView1.frame = CGRectMake(10.0, 10.0, imageSize.width*1.2, imageSize.height);

// vertical stretch
imageView2.frame = CGRectMake(10.0, imageView1.frame.origin.y + imageView1.frame.size.height + 10.0, imageSize.width, imageSize.height*1.2);

// middle stretch
imageView3.frame = CGRectMake(imageView1.frame.origin.x + imageView1.frame.size.width + 10.0, 10.0, 450.0, 450.0);

[self.view addSubview:imageView1];
[self.view addSubview:imageView2];
[self.view addSubview:imageView3];