Cannot edit photo in Preview?

[pax-eterna]

So, all I am trying to do is simply reduce the size of a screen grab so it's the correct size for a forum...

I read that Preview is supposed ti be able to do that, however the Edit icon is greyed out...anyone know why this would be?

Is there another simple app (in macOS - don't want to have to d/l anything) I could use instead?

 

[HDFan]

reduce the size of a screen grab

in terms of dimensions or file size? You can change the latter via Files/Export.

 

[Spacetime Anomaly]

To change the size of a document:
Tools > Adjust size.

To crop:
Draw out a selection. Click the 'Show Markup Toolbar' option in the toolbar (a circle around a pen nib). Click the 'Crop To Selection' icon (the icon furthest right).