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Task/Xiaolin-Wus-line-algorithm/PureBasic/xiaolin-wus-line-algorithm.purebasic

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+Macro PlotB(x, y, Color, b)
+  Plot(x, y, RGB(Red(Color) * (b), Green(Color) * (b), Blue(Color) * (b)))
+EndMacro
+
+Procedure.f fracPart(x.f)
+  ProcedureReturn x - Int(x)
+EndProcedure
+
+Procedure.f invFracPart(x.f)
+  ProcedureReturn 1.0 - fracPart(x)
+EndProcedure
+
+Procedure drawAntiAliasedLine(x1.f, y1.f, x2.f, y2.f, color)
+  Protected.f dx, dy, xend, yend, grad, yf, xgap, ix1, iy1, ix2, iy2
+  Protected x
+
+  dx = x2 - x1
+  dy = y2 - y1
+  If Abs(dx) < Abs(dy)
+    Swap x1, y1
+    Swap x2, y2
+    Swap dx, dy
+  EndIf
+
+  If x2 < x1
+    Swap x1, x2
+    Swap y1, y2
+  EndIf
+
+  grad = dy / dx
+
+  ;handle first endpoint
+  xend = Round(x1, #pb_round_nearest)
+  yend = y1 + grad * (xend - x1)
+  xgap = invFracPart(x1 + 0.5)
+  ix1 = xend  ;this will be used in the MAIN loop
+  iy1 = Int(yend)
+  PlotB(ix1, iy1, color, invFracPart(yend) * xgap)
+  PlotB(ix1, iy1 + 1, color, fracPart(yend) * xgap)
+  yf = yend + grad ;first y-intersection for the MAIN loop
+
+  ;handle second endpoint
+  xend = Round(x2, #pb_round_nearest)
+  yend = y2 + grad * (xend - x2)
+  xgap = fracPart(x2 + 0.5)
+  ix2 = xend  ;this will be used in the MAIN loop
+  iy2 = Int(yend)
+  PlotB(ix2, iy2, color, invFracPart(yend) * xgap)
+  PlotB(ix2, iy2 + 1, color, fracPart(yend) * xgap)
+  ;MAIN loop
+  For x = ix1 + 1 To ix2 - 1
+    PlotB(x, Int(yf), color, invFracPart(yf))
+    PlotB(x, Int(yf) + 1, color, fracPart(yf))
+    yf + grad
+  Next
+EndProcedure
+
+Define w = 200, h = 200, img = 1
+CreateImage(img, w, h) ;img is internal id of the image
+
+OpenWindow(0, 0, 0, w, h,"Xiaolin Wu's line algorithm", #PB_Window_SystemMenu)
+
+StartDrawing(ImageOutput(img))
+  drawAntiAliasedLine(80,20, 130,80, RGB(255, 0, 0))
+StopDrawing()
+
+ImageGadget(0, 0, 0, w, h, ImageID(img))
+
+Define event
+Repeat
+  event = WaitWindowEvent()
+Until event = #PB_Event_CloseWindow