A position is a pixel location within a viewport. The upper-left corner is pixel (0, 0), and positions increase to the right and down.
Represents a positions.
Returns the color of the pixel at position p in viewport; 0 denotes white and 1 denotes not white.
Returns an rgb value for color of the pixel at position p in viewport.
|((test-pixel viewport) color) → rgb?|
|viewport : viewport?|
Returns the color that will actually be used if color is used to draw.