`image-ref``i``p`procedureIndex into an PNM image or into a matrix. This is like indexing into a matrix except that the arguments are reversed. A

*matrix-ref*takes the row and then the column, image-ref takes a point which is an (x,y) coordinate.

`image-ref``i``p`procedureIndex into an PNM image or into a matrix. This is like indexing into a matrix except that the arguments are reversed. A

*matrix-ref*takes the row and then the column, image-ref takes a point which is an (x,y) coordinate.