Issue with reading images (video frames) from a folder?

I am trying to read images from scene_0001.bmp to scene_0062.bmp for Proper orthogonal decomposition. I am getting no output.

% Import the images from folder. The images are extracted from the Schlieren 
% video for wedge_4_68 at Mach 2.5.  
data = [];
% if strcmp(example,'cylinder')
    directory = '4_68_image';
    count = 1;
    while exist(sprintf('%s/scene_%0.4d.bmp',directory,count)) ~= 0
        data(:,:,count) = imread(sprintf('%s/scene_%0.4d.bmp',directory,count));
        count = count +1;
    end
    r = size(data,1); c = size(data,2);
    % Transform the data into column vectors.
    data=reshape(data,r*c,size(data,3)); 

[Walter Roberson]

Duplicates https://www.mathworks.com/matlabcentral/answers/876058-why-does-the-following-function-produce-error-index-in-position-2-exceeds-array-bounds#comment_1632843