Make screen shots and icon high resolution

[shahabfk]

Hi,

I have extension with icon and screen shots.

Recommended size for extension icon is 450 px x 450 px and maximum dimension is 700 px x 680 px for screen shots
as per document 0448_Connect_DevStyleguide_v6.pdf

I want to make my icon and screen resize as per above sizes with high resolution.

How to resize images and keep in high resolution.

I am developer with little knowledge about photoshop.

Any idea?