static void drawLine(BufferedImage image, int x1, int y1, int x2, int y2, Color color) {
  drawLine(imageGraphics(image), x1, y1, x2, y2, color);
}

static void drawLine(Graphics2D g, int x1, int y1, int x2, int y2, Color color) {
  g.setColor(color);
  g.drawLine(x1, y1, x2, y2);
}

static void drawLine(BufferedImage image, Pt a, Pt b, Color color) {
  drawLine(imageGraphics(image), a, b, color);
}

static void drawLine(Graphics2D g, Pt a, Pt b, Color color) {
  drawLine(g, a.x, a.y, b.x, b.y, color);
}

ifclass DoubleEdge

import java.awt.geom.Line2D;
static void drawLine(Graphics2D g, DoubleEdge e, Color color) {
  if (e == null) ret;
  g.setColor(color);
  g.draw(new Line2D.Double(e.x1(), e.y1(), e.x2(), e.y2()));
}
endif

Began life as a copy of #1006925