i think this is an image_quad bug, the optional from parameters are incorrectly scaled, i think by a factor of 2.
for example
image_quad('iob:alert_256',0,0, 256,0,0,256, 256,256,0,0,256,0,0,256,256,256)
produces a clipped image. note, you could also use image with the from parameters if you are just trying to crop. image_quad is for drawing warped quadrilaterals, regular image works fine for rectangles.
(img, siz) = render_text('9','Helvetica',100) rect(pos[0],pos[1],siz[0]-6,siz[1]-40) tint(0,0,0) image(img, pos[0], pos[1],siz[0]-6,siz[1]-40,3,20,siz[0]-6,siz[1]-40)