Drawing thick lines with dot projection …

public void drawThickLine(Graphics g, int x1, int y1, int x2, int y2, int thickness) {
// The thick line is in fact a filled polygon
int dX = x2 - x1;
int dY = y2 - y1;
// line length
double lineLength = Math.sqrt(dX * dX + dY * dY);
double scale = (double)(thickness) / (2 * lineLength);

// The x,y increments from an endpoint needed to create a rectangle...
double ddx = -scale * (double)dY;
double ddy = scale * (double)dX;
ddx += (ddx > 0) ? 0.5 : -0.5;
ddy += (ddy > 0) ? 0.5 : -0.5;
int dx = (int)ddx;
int dy = (int)ddy;

// Now we can compute the corner points...
int xPoints[] = new int[4];
int yPoints[] = new int[4];

xPoints[0] = x1 + dx; yPoints[0] = y1 + dy;
xPoints[1] = x1 - dx; yPoints[1] = y1 - dy;
xPoints[2] = x2 - dx; yPoints[2] = y2 - dy;
xPoints[3] = x2 + dx; yPoints[3] = y2 + dy;

g.drawFilledPath(xPoints, yPoints, null, null);
}

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