Need help incrementally nameing files as it saves in a loop

So let me premept this by saying I am in every single way an amateur with matlab. I am developing a code that will enable me to crop a series of images in a folder with a standardized crop size, then save the cropped images with a new name to a new folder. The entire code is working (albeit probably inefficient and poorly) aside from the renaming aspect of it.

%operating all pictures in a folder
clear all
close all
clc

dname_open = input('Please Enter the Directory Address of the Images:','s');
dname_save = input('Please Enter the Directory Address of the Save Destination:', 's');

%Code Test parameter (Will only do first image in folder if test=1)
test = 0;

%Set up basic file name path to be read
top_file = [dname_open '\'];
ls_top_file = ls(top_file);
c = cellstr(ls_top_file);
cc = c(3:length(c));
S = size(cc);
a = 1;
S(1)

%Input image for crop coordinates
    close all
    file = char(cellstr([top_file char(cc(a))]));
    data_n = char(cc(a));
    file_name = char(cc(a));
imagename = (file_name)
fileToRead2 = [dname_open '\' imagename];

I = imread(fileToRead2);

[I1c rect]= imcrop(I)
I2 = imcrop(I, rect);
imshow (I2, 'Border', 'Tight');

set(gcf, 'Position', [0 0 1 1]);
h = gcf;
saveas(h, [dname_save '\' 'IMG_' '001'], 'jpg')

%Crop Loop
while a<= S(1)
    close all
    file = char(cellstr([top_file char(cc(a))]));
    data_n = char(cc(a));
    file_name = char(cc(a));

% Operations on files
imagename = (file_name);
newname= sprintf('%d IMG_');

%Input image
fileToRead2 = [dname_open '\', imagename];

I = imread(fileToRead2);

%Cropping
%Vector [xmin, ymin, width, height]
I2 = imcrop(I, rect);
imshow(I2,'Border','Tight');

set(gcf, 'PaperPositionMode', 'auto');
h = gcf;
saveas(h, [dname_save '\' 'IMG_', a], 'jpg');

if test == 1
    fprintf('breaking loop to set axis - test==1')
    break
end
a=a+1
end

The error lies in "saveas(h, [dname_save '\' 'IMG_', a], 'jpg');" of this code. It won't work using "a" to increment the save name, but works fine when I use the variable "imagename"

Any help would be greatly appreciated.

Answer 1

[Star Strider]

I didn’t run your code so you have to do this experiment. See if:

saveas(h, [dname_save '\' 'IMG_', num2str(a,'%d')], 'jpg');

improves things.

[Shant]

Worked like a charm... Thanks!

[Star Strider]

My pleasure!

[per isakson]

An alternative

    saveas( h, fullfile( dname_save, sprintf( 'IMG_%03d.jpg', a ) ) );

The format specifier, &nbsp %03d, &nbsp with leading zeros make the names easier to use in Windows Explorer.