// This macro divides a circular selection
// into a set of slices (like pie slices).
// Author: Johannes Schindelin

// get the center and radii
getSelectionBounds(x, y, width, height);
radiusX = width / 2;
radiusY = height / 2;
centerX = x + radiusX;
centerY = y + radiusY;

// ask the user how many slices she wants
pieSliceCount = getNumber("How many slices?", 4);
angleSteps = 2 * PI * (radiusX + radiusY) / 4 / pieSliceCount;

// make the slices and add them to the ROI Manager
for (i = 0; i < pieSliceCount; i++) {
	startAngle = 2 * PI * i / pieSliceCount;
	endAngle = 2 * PI * (i + 1) / pieSliceCount;
	x = newArray(angleSteps + 2);
	y = newArray(angleSteps + 2);
	for (step = 0; step <= angleSteps; step++) {
		angle = startAngle + (endAngle - startAngle)
			* step / angleSteps;
		x[step] = centerX + radiusX * cos(angle);
		y[step] = centerY + radiusY * sin(angle);
	}
	x[angleSteps + 1] = centerX;
	y[angleSteps + 1] = centerY;
	makeSelection("freehand", x, y);
	roiManager("Add");
}