(bitmap-clearpixel! <bitmap> <row> <column>) sets the pixel at the given row and column to zero (white). The bitmap is modified and returned.
[1] (define bitmap (bitmap-create 1 1))
bitmap
[2] (bitmap-clearpixel! bitmap 0 0)
#<bitmap orow:-1 ocol:-1 xres:-1 yres:-1 h:1 w:1>
[3] (bitmap-clearpixel! bitmap 0 1)
ERROR!
message : error (dimension?)
irritant : #<primitive-procedure bitmap-clearpixel!>
expression: 1
continue : possible, continue with value as value from primitive
Error (? for help) >>