Matlab image translation matrix - matlab

Question

I'm very new to Matlab. I'm learning some image manipulation basics, and I'm a bit confused on how to write a translation without using imtranslate.
this is my code but it just displays a black background. Thank you.
img = imread('name2.png');
figure(1);
% pixel matrix
[orig_x, orig_y,z] = size(img);
final_x = 600;
final_y = 600;
% define the final array with calculated dimensions and fill the array with zeros ie.,black
final_img = uint8(zeros([final_x final_y 3 ]));
for i = 1 : size(final_img, 1)
for j = 1 : size(final_img, 2)
new_x = img(i) + 5;
new_y = img(j) + 5;
% fprintf('X: %f\n',new_x); % prints 255
final_img(i) = new_x;
final_img(j) = new_y;
end
end
imshow(final_img);

Answer 1

This is one solution for 'translation only' transformation.
I = imread('Lenna.png');
shiftX = 5; % shift columns
shiftY = 5; % shift rows
% Assigning empty matrix for result, expected to be shiftX-1 larger in rows and shiftY-1 larger in columns
nI = uint8( zeros(size(I,1)+shiftY-1, size(I,2)+shiftX-1, size(I,3));
% Translate
nI(shiftY:end, shiftX:end, :) = I;
imshow(nI)
Now the image will start from (x,y) = (5,5) instead of (1,1). Also note that in matlab image coordinate system, x and y axis start from upper left corner (documentation).

Answer 2

final_img:
You've defined "final_img" with new x and new y but you haven't replaced the zeros in the red/green/blue values. It's all black because of your initialisation filling the final_img with all zeros.
Maybe try this instead of what you've written:
%{
[X,map] = imread('name2.png');
figure(1);
% X should be 600 by 600
%Translate X however you wish, e.g.:
X = X +5;
%Verify that the colormap, map, is not empty, and convert
%the data in X to RGB and store as your final_img.
if ~isempty(map)
final_img = ind2rgb(X,map);
end
%}
I am also not sure if you want to be indexing img with just a single i without the the other dimensions like you have:
new_x = img(i) + 5;
?

Answer 3

For the problems in your specific code, I wrote in the comments some of them.
A short way to achieve image translation is by 2D convolution with a filter of zeros and just one 1, that will preserve the values of the image, but relocate them according to the size of the filter and the position of the 1 in it.
That seems you want to move the image but preserve the size of the total image, if I get it right. So:
r=3; c=5; % number of rows and columns to move
filt=zeros(r*2+1, c*2+1); filt(end)=1; % the filetr
img2=conv2(img,filt,'same'); % the translated image
Just for the example, lets translate "cameraman" with 20 rows and columns:
img=imread('cameraman.tif');
imshow(img)
r=20; c=20;
filt=zeros(r*2+1, c*2+1); filt(end)=1;
img2=conv2(img,filt,'same');
figure; imshow(img2,[])