I think I found the solution :
PlanarImage src = JAI.create("fileload", "Photo.jpg");
System.out.println(src.getColorModel());
double[][] matrix = {
{ 1.0D, 0.0D },
{ 1.0D, 0.0D },
{ 1.0D, 0.0D }
};
ParameterBlock pb = new ParameterBlock();
pb.addSource(src);
pb.add(matrix2);
// Perform the band combine operation.
PlanarImage dst = (PlanarImage)JAI.create("bandcombine", pb, null);
System.out.println(dst .getColorModel());