Resizing a PSD File

While Photoshop Can resize your assets for those Aspect Ratios and sizes you would most likely not find the resizing acceptable.   Photoshop's Content aware scale will distort your content appearance.

Depending on what you, and they, mean, it's either easy or impossible. There is no middle ground. It's like saying "can I fit make a rectangle into a square without distortion".

- if you want to fill the entire design, of course not. You have to cut something off, or stretch it out of shape

- if you want it WITHIN a space, sure you can, by adding white space, or something more imaginative. 

You NEEDED this to be part of the spec. Otherwise, it's many more hours of unbillable design work.

Your designers are correct. If you think about it for a minute, the proportions of each size are different so you can’t resize your aspect ratio without squishing or stretching the content. For example, to change the Eventbrite pixel dimensions to the Meetup size, you could adjust the width to 1200 but the height would be 594, not the 675 pixels you need. A quick illustration of these sizes shows how the content will have to be adjusted for each new size. You can also crop or extend the background as suggested below!

What you are asking is possible but would mean designing separate files for each platform as they are not proportional to each other.

No you cannot.

The aspect ratio of the original (i.e. the ratio between the height and the width) is different to the aspect ratio in your proposed sizes. So you would have three choices :

1. Distort the image so it fits the required aspect ratios

or

2. Crop some of the image so the remainder fits in the changed aspect ratios

or

3. Add to the image so that the extended image fits the new aspect ratios

Dave