php exec() command doesn't work with other application

Question

I have an application which was developed using php and I want to print a dithering image through my printer so what I am doing is I have an application called ImageMagick. In this application using command prompt I will pass an image path and the destination folder. So when I run the command in the command prompt it will convert the image and save it in destination folder.

Firstly I tried the php exec() for the below code

    <?php
     echo exec('ipconfig');
    ?>

The above code gives the output on the browser

When I give the below code:

   <?php
     echo exec('date');
   ?>

It gives the output as below

Enter the new date: (mm-dd-yy)

But When I run the date command on the command prompt it gives the current date

I tried to run the Imagemagick command in php code as shown below

<?php
echo exec('convert "C:\bhargav\dev\download.jpg" -resize 384 -dither FloydSteinberg -remap pattern:gray50 "C:\bhargav\dev\con.jpg"');
?>

But it doesn't save any image as output and no error is shown on the browser.

convert "C:\bhargav\dev\download.jpg" -resize 384 -dither FloydSteinberg -remap pattern:gray50 "C:\bhargav\dev\con.jpg"

when the above command is given in the command prompt it gives me the output.

Where am I going wrong?