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I am trying to follow specs for iTunes app graphic.

The requirements state:
72ppi, rgb,flattended, NO transparency High qualtiy PNG plus 8-bit alpha.

Everything I read about alpha is WITH transparency. How do I meet their specs?

  • Alpha refers to a mask in this instance. 8 bit.. black and white mask of the image. – Scott Apr 16 '14 at 21:07
  • Scott, can you be more specific? Is this something I have to do in the file itself or a step when I am saving? – Terri Apr 16 '14 at 21:08
  • @terri: It is important to check the pixel specs in the link in Scott's answer. "72ppi" does not make sense as a specification and it does not appear anywhere on that specification page. Ignore "ppi" and "dpi" and focus on actual pixel dimensions. – horatio Apr 16 '14 at 21:50
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In this instance the "alpha" is referring to a mask channel, not directly meaning transparency in the image itself depending upon the software being used.

What they are actually asking for is a PNG32 format. A 24-bit PNG + 8 bits for transparency. Apple is trying to be diplomatic and state things in the lowest common denominator rather than referring to one specific piece of image software.

Within Photoshop, transparency adds the alpha to a PNG file. You can't directly save an independent alpha channel in the PNG format.

Using Photoshop, simply create an RGB image with transparency, then use Save for Web to save the file as a PNG24. This will result in a 24-bit PNG with 8-bits of alpha (32bit PNG).

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