Hi Raphael, it is difficult to give exact solution without your data, but you can use the example code below which superimposes edge data over an RGB image.
clear; clc; close all;
% Read the RGB image
peppers = imread('peppers.png'); % Read your image here
% Load the edge data from the .mat file
load edgeData.mat; % Read your mat file here
% Show the RGB image
figure; imshow(peppers);
% Make a solidwhite patch
white = cat(3, ones(size(edgePeppers)),ones(size(edgePeppers)), ones(size(edgePeppers)));
% Lay the solid white patch over the RGB image
hold on; h = imshow(white); hold off;
% Use the edge data pixels to control the transparency of each pixel in the white image
set(h, 'AlphaData', edgePeppers);
Hope this helps!