How to write an array as an image that uses the full range of colors in the colormap in matlab as a .tif file of 256x256 size????

I writing a program for forward scattering in image reconstruction .Can any one help me in finding How to write an array as an image that uses the full range of colors in the colormap in matlab as a .tif file of 256x256 size????

The output images are displayed as follows. i want to use these images for another part of my program which is written as a new script.

figure(2);
imagesc(param.x(1,:),param.y(:,1),real(E_matrix));title('Real Part')
colormap(jet);colorbar;grid on;
%% Plotting Imag Part
figure(3)
imagesc(param.x(1,:),param.y(:,1),imag(E_matrix));title('Imag Part')
colormap(jet);colorbar;grid on;