Question

By default, UIImageView displays his image as 1px of image = 1pt in UIImageView, but I’d like to display as 2px of image = 1pt.

Version of saving image with name “..@2x..” is not suitable, images are not saving in file system.

For example, image size is 400×100, I want to display the image on center of display, and it should be 120 pt on the left and 120 pt on the right of the image(640-400) / 2

Answer 1

That’s quite easy, note that for the versions below iOS 4 you don’t have Retina displays, that’s why in the image scaling method i’m doing this check first:

//Retina detect
    if ([[UIScreen mainScreen] respondsToSelector:@selector(scale)] && [[UIScreen mainScreen] scale] == 2){

and then having image loaded from somewhere (file, cache, etc.) i’m scaling it this way

UIImage * image2Xscaled = [UIImage alloc];
            image = [[image2Xscaled initWithCGImage:[image CGImage] scale:2.0 orientation:UIImageOrientationUp] autorelease];

The method

initWithCGImage:scale:orientation:

is available at iOS 4.0. that’s why you need the first check. If sale is not supported, return the 1.0 scaled image.