func drawCell(feat *rimg64.Multi, i, j int, gc *draw2d.ImageGraphicContext, cell int) { u := (float64(i) + 0.5) * float64(cell) v := (float64(j) + 0.5) * float64(cell) r := float64(cell) / 2 for k := 0; k < Orientations; k++ { x := feat.At(i, j, k) x = math.Max(x, 0) x = math.Min(x, 1) gc.SetStrokeColor(color.Gray{uint8(x*254 + 1)}) theta := (0.5 + float64(k)/float64(Orientations)) * math.Pi drawOrientedLine(gc, u, v, theta, r) } }