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I'm trying to create an iPhone wallpaper from an image. (iPhone 4, retina display)

I've already found the resolution, which is 640 x 960, but the problem is that when I export the image out of Pixelmator (Mac alternative of Photoshop – similar to GIMP), the image looks fine, but the text that I've put is very blurry / pixellated.

I've increased DPI to 320, but the text still looks terrible.

What am I doing wrong?

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Can you post a sample image for us to look at? –  DA01 Mar 12 '12 at 19:27
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2 Answers 2

DPI/PPI doesn't matter. The only thing that counts is the pixel resolution, which you already have correct if you're using 640 × 960.

Increasing the image to 326PPI and keeping the resolution to 640 × 960 will do nothing. DPI/PPI is just a tag that's associated with the document.

Pixelmator uses OS X standard text rendering, so it should look as good as possible. It sounds like your text may be very small though? Have you tested the wallpaper on an iPhone itself? Can you please upload the full image so I can take a look at it?

There's not anything special that needs to be done. Just create a document that's 640 × 960, design whatever you'd like and save it as a 24bit PNG.

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OS X's native font rendering uses subpixel AA, which is not possible to reproduce in static images since the AA algorithm depends on the specific subpixel geometry of the display it's being displayed on. So unless he's exporting the image as an SVG or other vector format, it's not going to use OS X's text rendering engine. –  Lèse majesté Mar 12 '12 at 6:58
    
@Lèsemajesté: While not good practice, surely if you do create text in a static image using OS X's RGB subpixel rendering, it will display the same way on any other device using the same sequence of R, G, B subpixel elements. –  e100 Mar 12 '12 at 14:13
    
@e100: Sure, but then it's only proper subpixel rendering on those specific devices, and on all other devices, it's just randomly colorized pixels. This is especially pertinent when designing for mobile devices, where even if the subpixel geometry is the same, the image could be displayed in the wrong orientation. –  Lèse majesté Mar 13 '12 at 11:02
    
Ah yes, orientation is a big factor –  e100 Mar 13 '12 at 12:17
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Looks like the app that I was using to transfer the image to my iPhone added some compression and decreased the image quality. (Dropbox, before an update removed this feature)

Thanks for all the response though!

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