update

Task/Bitmap-Bresenhams-line-algorithm/FBSL/bitmap-bresenhams-line-algorithm.fbsl

@@ -0,0 +1,35 @@
+#DEFINE WM_LBUTTONDOWN 513
+#DEFINE WM_CLOSE 16
+
+FBSLSETTEXT(ME, "Bresenham") ' Set form caption
+FBSLSETFORMCOLOR(ME, RGB(0, 255, 255)) ' Cyan: set persistent background color
+DRAWWIDTH(5) ' Adjust point size
+FBSL.GETDC(ME) ' Use volatile FBSL.GETDC below to avoid extra assignments
+
+RESIZE(ME, 0, 0, 200, 235)
+CENTER(ME)
+SHOW(ME)
+
+BEGIN EVENTS
+	SELECT CASE CBMSG
+		CASE WM_LBUTTONDOWN: Rhombus() ' Draw
+		CASE WM_CLOSE: FBSL.RELEASEDC(ME, FBSL.GETDC) ' Clean up
+	END SELECT
+END EVENTS
+
+SUB Rhombus()
+	Bresenham(50, 100, 100, 190)(100, 190, 150, 100)(150, 100, 100, 10)(100, 10, 50, 100)
+	
+	SUB Bresenham(x0, y0, x1, y1)
+		DIM dx = ABS(x0 - x1), sx = SGN(x0 - x1)
+		DIM dy = ABS(y0 - y1), sy = SGN(y0 - y1)
+		DIM tmp, er = IIF(dx > dy, dx, -dy) / 2
+		
+		WHILE NOT (x0 = x1 ANDALSO y0 = y1)
+			PSET(FBSL.GETDC, x0, y0, &HFF) ' Red: Windows stores colors in BGR order
+			tmp = er
+			IF tmp > -dx THEN: er = er - dy: x0 = x0 + sx: END IF
+			IF tmp < +dy THEN: er = er + dx: y0 = y0 + sy: END IF
+		WEND
+	END SUB
+END SUB

Task/Bitmap-Bresenhams-line-algorithm/Racket/bitmap-bresenhams-line-algorithm.rkt

@@ -0,0 +1,33 @@
+#lang racket
+(require racket/draw)
+
+(define (draw-line dc x0 y0 x1 y1)
+  (define dx (abs (- x1 x0)))
+  (define dy (abs (- y1 y0)))
+  (define sx (if (> x0 x1) -1 1))
+  (define sy (if (> y0 y1) -1 1))
+  (cond
+    [(> dx dy)
+     (let loop ([x x0] [y y0] [err (/ dx 2.0)])
+       (unless (= x x1)
+         (send dc draw-point x y)
+         (define newerr (- err dy))
+         (if (< newerr 0)
+             (loop (+ x sx) (+ y sy) (+ newerr dx))
+             (loop (+ x sx)    y        newerr))))]
+    [else
+     (let loop ([x x0] [y y0] [err (/ dy 2.0)])
+       (unless (= y y1)
+         (send dc draw-point x y)
+         (define newerr (- err dy))
+         (if (< newerr 0)
+             (loop (+ x sx) (+ y sy)    newerr)
+             (loop    x     (+ y sy) (+ newerr dy)))))]))
+
+(define bm (make-object bitmap% 17 17))
+(define dc (new bitmap-dc% [bitmap bm]))
+(send dc set-smoothing 'unsmoothed)
+(send dc set-pen "red" 1 'solid)
+(for ([points '((1 8 8 16) (8 16 16 8) (16 8 8 1) (8 1 1 8))])
+  (apply draw-line  (cons dc points)))
+bm