function histogram(which) {
	document.getElementById('hist_rgb').style.display = 'none';
	document.getElementById('hist_r').style.display = 'none';
	document.getElementById('hist_g').style.display = 'none';
	document.getElementById('hist_b').style.display = 'none';

	document.getElementById('hist_'+which).style.display = 'block';
}