Question

I have an app that does a screen capture on a retina-iPad (iPad3.) Or maybe I just do the screen capture with HOME+POWER and get the image that way, it doesn’t matter. In the end, I have a captured image that is 2048×1536 — that’s 1024×768 @2x.

Now I want to display this image — this 2048×1536 image — back on the screen and I want to preserve the lovely retina-ness of it.

When I do something like this (code typed in web browser):

UIImage *myImage = [UIImage imageWithContentsOfFile: pathToMyHiresImage];
UIImageView *myImageView = [[UIImageView alloc] initWithImage: myImage];
myImageView.frame = screenBounds;  // make it fit
// etc...

I end up with a low-rez (jaggy diagonal lines & text) version of the image.

So my question is: what do I have to do in order to display that image back on the screen and get it to display @2x-DPI, so it has that pretty retina-look?

Thanks!

Answer 1

This should do the trick:

UIImage *myImage = [UIImage imageWithContentsOfFile: pathToMyHiresImage];
// *****Added Code*****
myImage = [UIImage imageWithCGImage:myImage.CGImage scale:2 orientation:myImage.imageOrientation];
// ********************
UIImageView *myImageView = [[UIImageView alloc] initWithImage: myImage];
myImageView.frame = screenBounds;  // make it fit
// etc ...

Good luck!

EDIT (Olie)
Here is the final code, taking DavidH’s suggestion into account:

UIImage *myImage = [[UIImage alloc] initWithContentsOfFile: path];

if ([[UIScreen mainScreen] respondsToSelector: @selector(scale)])
{
    float screenScale = [[UIScreen mainScreen] scale];
    if (screenScale > 1.)
    {
        id oldImage = myImage;
        myImage = [[UIImage imageWithCGImage: myImage scale: screenScale orientation: myImage.imageOrientation] retain];
        [oldImage release];
    }
}