Try this:
imwrite(yourImageMatrix, var1);
It would be good to add an extension so that it knows the format to write it out in. If var1 does not contain the extension, like 1.jpg, then append an extension and prepend the folder where you want to store the image:
var1 = '1234'; % Whatever - some filename with or without extension.
[~, baseFileName, ext] = fileparts(var1);
if isempty(ext)
ext = '.PNG'; % Make it a PNG format image.
end
fullFileName = fullfile(yourFolder, [baseFileName, ext]);
imwrite(yourImageMatrix, fullFileName);
