Data commit

Task/Bitmap-Midpoint-circle-algorithm/Go/bitmap-midpoint-circle-algorithm-1.go

@@ -0,0 +1,36 @@
+package raster
+
+// Circle plots a circle with center x, y and radius r.
+// Limiting behavior:
+// r < 0 plots no pixels.
+// r = 0 plots a single pixel at x, y.
+// r = 1 plots four pixels in a diamond shape around the center pixel at x, y.
+func (b *Bitmap) Circle(x, y, r int, p Pixel) {
+    if r < 0 {
+        return
+    }
+    // Bresenham algorithm
+    x1, y1, err := -r, 0, 2-2*r
+    for {
+        b.SetPx(x-x1, y+y1, p)
+        b.SetPx(x-y1, y-x1, p)
+        b.SetPx(x+x1, y-y1, p)
+        b.SetPx(x+y1, y+x1, p)
+        r = err
+        if r > x1 {
+            x1++
+            err += x1*2 + 1
+        }
+        if r <= y1 {
+            y1++
+            err += y1*2 + 1
+        }
+        if x1 >= 0 {
+            break
+        }
+    }
+}
+
+func (b *Bitmap) CircleRgb(x, y, r int, c Rgb) {
+    b.Circle(x, y, r, c.Pixel())
+}

Task/Bitmap-Midpoint-circle-algorithm/Go/bitmap-midpoint-circle-algorithm-2.go

@@ -0,0 +1,21 @@
+package main
+
+// Files required to build supporting package raster are found in:
+// * This task (immediately above)
+// * Bitmap
+// * Write a PPM file
+
+import (
+    "raster"
+    "fmt"
+)
+
+func main() {
+    b := raster.NewBitmap(400, 300)
+    b.FillRgb(0xffdf20) // yellow
+    // large circle, demonstrating clipping to image boundaries
+    b.CircleRgb(300, 249, 200, 0xff2020) // red
+    if err := b.WritePpmFile("circle.ppm"); err != nil {
+        fmt.Println(err)
+    }
+}