Question

I just wanted to know if my image has x*y dimensions.

When retina display devices show that image created with a CGRectMake(0,0,x,y), would that be a pixelated image?

Should the correct size have been CGRectMake(0,0,x/2,y/2)?

How can I tell the rect size that an image should have?

Do I need to use the contentScaleFactor = [UIScreen mainScreen].scale;?

or maybe divide by it as in: CGRectMake(0,0,x/contentScaleFactor,y/contentScaleFactor)?

Answer 1

Dimensions are measured in points instead of pixels. Both retina and non-retina display devices have the same points. On a non-retina display device, one point equals one pixel, but on a retina display device, one point equals two pixels. So, you will use CGRectMake(0,0,x,y) for both.

To avoid a pixelated image, make sure to provide a double-resolution image with the @2x suffix. For example, if your regular image was named foo.png, then the retina version should be named [e-mail].

When coding, refer to foo.png at all times. When your app is running on a retina display device the double-resolution image ([e-mail]) will be used automatically.