function bresLine(sequence screenData, integer x0, integer y0, integer x1, integer y1, integer colour)
-- The line algorithm
integer deltaX = abs(x1-x0),
        deltaY = abs(y1-y0),
        stepX = iff(x0<x1,1,-1),
        stepY = iff(y0<y1,1,-1),
        lineError = iff(deltaX>deltaY,deltaX,-deltaY),
        prevle

    lineError = round(lineError/2,1)
    while 1 do
        if x0>=1 and x0<=length(screenData)
        and y0>=1 and y0<=length(screenData[x0]) then
            screenData[x0][y0] = colour
        end if
        if x0=x1 and y0=y1 then exit end if
        prevle = lineError
        if prevle>-deltaX then
            lineError -= deltaY
            x0 += stepX
        end if
        if prevle<deltaY then
            lineError += deltaX
            y0 += stepY
        end if
    end while
    return screenData
end function

sequence screenData = new_image(400,300,black)
    screenData = bresLine(screenData,100,1,50,300,red)
    screenData = bresLine(screenData,1,180,400,240,green)
    screenData = bresLine(screenData,200,1,400,150,white)
    screenData = bresLine(screenData,195,1,205,300,blue)
    write_ppm("bresenham.ppm",screenData)