Think of the background image as a sheet of graph paper with the origin (0,0) in the bottom left corner.
The numbers in put-image specify a point on that graph paper, where the center of the top image should be placed.
The width of the rectangle is 300 and the height is 200. The definitions for dot and background are:
(define dot (circle 50 "solid" "red"))
(define background (rectangle 300 200 "outline" "black"))
Estimate: What coordinates for the dot would create each of the following images?
A |
B |
||
(put-image dot background) |
(put-image dot background) |
||
C |
D |
||
(put-image dot background) |
(put-image dot background) |
These materials were developed partly through support of the National Science Foundation,
(awards 1042210, 1535276, 1648684, and 1738598). 
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