how to put border on the image over top and bottom

i have sucessfully implemented the border on left and right but unable to do on top and bottom

code that i have used for this program is

a = imread('imagea.jpg');
b = imread('imageb.jpg');
close all;
[y,x,c] = size(a);
c = uint8(zeros(y,10,c));
d=[a,c,b];
c(:,:,1) = 255;
d=[c,a,c,b,c];
imshow(d);

Out put result of this is like that

now i want border on top and bottom, but no progress

Answer 1

[Bryan]

could you not just do

plot([min(xlim) max(xlim)],[max(ylim) max(ylim)], 'r-', 'linewidth', 2)

plot([min(xlim) max(xlim)],[min(ylim) min(ylim)], 'r-', 'linewidth', 2)

Answer 2

[Akira Agata]

Assuming "imagea.jpg" and "imageb.jpg" have the same size, how about the following?

a = imread('imagea.jpg');
b = imread('imageb.jpg');

sz = size(a);

Iab = [a,b];

figure
imshow(Iab)
hold on
rectangle(...
  'Position', [1 1 sz(2)-1 sz(1)-1],...
  'LineWidth',2,...
  'EdgeColor','r')
rectangle(...
  'Position',[sz(2) 1 sz(2)-1 sz(1)-1],...
  'LineWidth',2,...
  'EdgeColor','r')