ImageMagick: possibly OT

[Bill Oliver]

On Thu, 17 Sep 2015, Timothy Murphy wrote:

> I want to crop a PNG picture.
> I see how to do it with ImageMagick,
> once I know the pixel-positions of the corners of the rectangle.
>
> I'm wondering if there is a way of imposing a grid to read these numbers,
> either with ImageMagick or some other application that runs under Fedora ?
>
>

I may not be understanding the problem, but if you just need the four
corners, e.g. 0,0; 0,1023; 1023,0, 1023,1023 for a 1024 x 1024 image, 
and you don't want to need to look at the image, try the netpbm library,
e.g.

$ pngtopnm < tst.png | pnmfile


billo