changed how masks are stored for massive performance improvment and way less ram usage

mask.go

@@ -0,0 +1,91 @@
+package main
+
+import "image"
+
+// PixelMask stores per-pixel occupancy using one byte per pixel.
+type PixelMask struct {
+	Width  int
+	Height int
+	Data   []uint8
+}
+
+func NewPixelMask(width, height int) *PixelMask {
+	if width <= 0 || height <= 0 {
+		return &PixelMask{}
+	}
+	return &PixelMask{
+		Width:  width,
+		Height: height,
+		Data:   make([]uint8, width*height),
+	}
+}
+
+func (m *PixelMask) index(x, y int) int {
+	return y*m.Width + x
+}
+
+func (m *PixelMask) InBounds(x, y int) bool {
+	return m != nil && x >= 0 && y >= 0 && x < m.Width && y < m.Height
+}
+
+func (m *PixelMask) GetXY(x, y int) bool {
+	if !m.InBounds(x, y) {
+		return false
+	}
+	return m.Data[m.index(x, y)] != 0
+}
+
+func (m *PixelMask) SetXY(x, y int) {
+	if m.InBounds(x, y) {
+		m.Data[m.index(x, y)] = 1
+	}
+}
+
+func (m *PixelMask) GetPoint(p image.Point) bool {
+	return m.GetXY(p.X, p.Y)
+}
+
+func (m *PixelMask) SetPoint(p image.Point) {
+	m.SetXY(p.X, p.Y)
+}
+
+func (m *PixelMask) Merge(other *PixelMask) {
+	if m == nil || other == nil || m.Width != other.Width || m.Height != other.Height {
+		return
+	}
+	for i := range m.Data {
+		if other.Data[i] != 0 {
+			m.Data[i] = 1
+		}
+	}
+}
+
+func (m *PixelMask) AddPoints(points []image.Point) {
+	for _, p := range points {
+		m.SetPoint(p)
+	}
+}
+
+func (m *PixelMask) ToPoints() []image.Point {
+	if m == nil {
+		return nil
+	}
+	pts := make([]image.Point, 0)
+	for y := 0; y < m.Height; y++ {
+		row := y * m.Width
+		for x := 0; x < m.Width; x++ {
+			if m.Data[row+x] != 0 {
+				pts = append(pts, image.Point{X: x, Y: y})
+			}
+		}
+	}
+	return pts
+}
+
+func BuildMaskFromLakes(width, height int, lakes [][]image.Point) *PixelMask {
+	mask := NewPixelMask(width, height)
+	for _, lake := range lakes {
+		mask.AddPoints(lake)
+	}
+	return mask
+}