Replicate alpha channel in Photoshop

Question

So I have two versions of a texture, one is low res and contains an alpha channel, and the other is high res and is missing the alpha channel. I was wondering whether it would be possible to recreate the alpha channel on the high resolution version in Photoshop.

Low res version (with alpha channel)

Taken in Photoshop to make alpha channel easier to see

High res version (no alpha channel)

Would it be possible to recreate the same or a similar alpha channel contained in the low res version on the high res one?

To help, here is a link containing the .psd file: https://drive.google.com/open?id=1UYsFFK0RyJa0xmOfKBbSCR3rDiVNCLjG

Answer 1

Yes it's possible, but the alpha channel will not be high resolution - it will be a bit blurry if you rescaled the image.

In your PSD, CTRL+Click (Command+Click on Mac) on the layer with alpha transparency. This will load the alpha channel as a selection.

Select, the layer without the alpha channel, then at the bottom of the layers panel hit the Add Layer Mask icon to create a layer mask. You can then delete the low res layer as it's not needed, or just hide it.

Example using your PSD

Answer 2

The essentials are already said in other answer. If you want sharper alpha channel, you should enlarge the low res image with proper enlargening software which doesn't make borders smoother. Examples:

• Smilla enlarger, freeware
• On1 Resize, premium priced commercial

Search for image enlarger software.