Using MATLAB to save a montage of many images as o

I am trying to save a montage of many (~500, 2MB each) images using MATLAB function imwrite, however I keep getting this error:

Error using imwrite>validateSizes (line 632)
Images must contain fewer than 2^32 - 1 bytes of data.
Error in imwrite (line 463)
validateSizes(data);

here is the code I am working with:

close all
clear all
clc
tic
file = 'ImageRegistrations.txt';
info = importdata(file);
ImageNames = info.textdata(:,1);
xoffset = info.data(:,1);
yoffset = info.data(:,2);
for i = 1:length(ImageNames);
ImageNames{i,1} = imread(ImageNames{i,1});
ImageNames{i,1} = flipud(ImageNames{i,1});
end
ImageNames = flipud(ImageNames);

for i=1:length(ImageNames)
    diffx(i) = xoffset(length(ImageNames),1) - xoffset(i,1);
end
diffx = (diffx)';
diffx = flipud(diffx);

for j=1:length(ImageNames)
    diffy(j) = yoffset(length(ImageNames),1) - yoffset(j,1);
end
diffy = (diffy)';
diffy = flipud(diffy);
matrix = zeros(max(diffy)+abs(min(diffy))+(2*1004),max(diffx)+abs(min(diffx))+(2*1002));
%matrix(1:size(ImageNames{1,1},1),1:size(ImageNames{1,1},2)) = ImageNames{1,1};
for q=1:length(ImageNames)
matrix((diffy(q)+abs(min(diffy))+1):(diffy(q)+abs(min(diffy))+size(ImageNames{q,1},1)),(diffx(q)+abs(min(diffx))+1):((diffx(q)+abs(min(diffx))+size(ImageNames{q,1},2)))) = ImageNames{q,1};
end

graymatrix = mat2gray(matrix);
graymatrix = flipud(graymatrix);
figure(2)
imshow(graymatrix)
imwrite(graymatrix, 'montage.tif')
toc

I use imwrite because it perserves the final montage in a full resolution file, whereas if I simply click save on the figure file it saves it as a low resolution file.

thanks!

Error does what it says on the tin, really. There is some sort of inbuilt limitation to input variable size in imwrite, and you're going over it.

Note that most images are stored as uint8 but I would guess that you end up with doubles as a result of your processing. That increases the memory usage.

It may be, therefore, that casting to another type would help. Try using im2uint8 (presuming your variable graymatrix is double, scaled between 0 and 1), before calling imwrite.