June 2018 Update

Task/Xiaolin-Wus-line-algorithm/Julia/xiaolin-wus-line-algorithm.julia

@@ -0,0 +1,75 @@
+using Images
+
+fpart(x) = mod(x, one(x))
+rfpart(x) = one(x) - fpart(x)
+
+function drawline!(img::Matrix{Gray{N0f8}}, x0::Integer, y0::Integer, x1::Integer, y1::Integer)
+    steep = abs(y1 - y0) > abs(x1 - x0)
+
+    if steep
+        x0, y0 = y0, x0
+        x1, y1 = y1, x1
+    end
+    if x0 > x1
+        x0, x1 = x1, x0
+        y0, y1 = y1, y0
+    end
+
+    dx = x1 - x0
+    dy = y1 - y0
+    grad = dy / dx
+
+    if iszero(dx)
+        grad = oftype(grad, 1.0)
+    end
+
+    # handle first endpoint
+    xend = round(Int, x0)
+    yend = y0 + grad * (xend - x0)
+    xgap = rfpart(x0 + 0.5)
+    xpxl1 = xend
+    ypxl1 = floor(Int, yend)
+
+    if steep
+        img[ypxl1,   xpxl1] = rfpart(yend) * xgap
+        img[ypxl1+1, xpxl1] =  fpart(yend) * xgap
+    else
+        img[xpxl1, ypxl1  ] = rfpart(yend) * xgap
+        img[xpxl1, ypxl1+1] =  fpart(yend) * xgap
+    end
+    intery = yend + grad # first y-intersection for the main loop
+
+    # handle second endpoint
+    xend = round(Int, x1)
+    yend = y1 + grad * (xend - x1)
+    xgap = fpart(x1 + 0.5)
+    xpxl2 = xend
+    ypxl2 = floor(Int, yend)
+    if steep
+        img[ypxl2,   xpxl2] = rfpart(yend) * xgap
+        img[ypxl2+1, xpxl2] =  fpart(yend) * xgap
+    else
+        img[xpxl2, ypxl2  ] = rfpart(yend) * xgap
+        img[xpxl2, ypxl2+1] =  fpart(yend) * xgap
+    end
+
+    # main loop
+    if steep
+        for x in xpxl1+1:xpxl2-1
+            img[floor(Int, intery),   x] = rfpart(intery)
+            img[floor(Int, intery)+1, x] =  fpart(intery)
+            intery += grad
+        end
+    else
+        for x in xpxl1+1:xpxl2-1
+            img[x, floor(Int, intery)  ] = rfpart(intery)
+            img[x, floor(Int, intery)+1] =  fpart(intery)
+            intery += grad
+        end
+    end
+
+    return img
+end
+
+img = fill(Gray(1.0N0f8), 250, 250);
+drawline!(img, 8, 8, 192, 154)