var N=400;
dessin=IJ.createImage("voronoi3p", "RGB", N, N, 1);
ip=dessin.getProcessor();
var A=[N/2,N/4];
var B=[N/8,4*N/5];
var C=[3*N/4,N/2];
ip.putPixel(A[0],A[1],0);
ip.putPixel(B[0],B[1],0);
ip.putPixel(C[0],C[1],0);
dessin.show();