Image Resolution question

hi
I am looking to develop a children's book app. I need help in understanding the resolution requirements and scaling. i Understand that the new ipad has a resolution of 2048-by-1536.

i am not a developer so please excuse my lack of knowledge.
the app i am planning to develop, i want the image to be in the middle with black borders on top and bottom. the black space is where the text of the book will be displayed. all the apps i have seen are full page and the written text appears on top of the image. so what would be the resolution of the image if i plan to leave about 3/4 of an inch space on top and bottom ? the artist can draw the image then based on those resolutions and i dont have to worry about stretching the image, etc.
is there a certain way to calculate this ? any help will be highly appreciated. Please see this quick wireframe for a better understanding.
Attachment 25878

cheers
khetani

If you divide the number of pixels in a dimension by the physical width or lenght of the screen (in inches) , you'll find out how many pixels make up an inch of the screen.

Rather than measure and divide, I cheated and looked up the resolution on the net :) Apple - The new iPad - View all the technical specifications.. The new iPad has 264 pixels per inch. So, if you want a .75 inch border, then it would be 264 pixels X .75 inches = 352 pixels wide..