I've never found the solution to pixelated images when applying a perspective envelope.

I have however, today, found a fix using a bit of logic.

I did my envelope as normal, then though if I want to increase the DPI use a filter and set it in the bar - it worked!

In the below example I used the Tilt Shift effect, but set to zero effect, which gave me the option to increase the resolution, which I did and it fixes everything perfectly.

Click image for larger version. 

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Now the question is, have I been missing something somewhere - because I did look through all the optioons and couldn't find anything?

Cheers

Chris