The image loading time can be reduced by reducing the image quality. This can be done from the server side in models/recipe.php line 50:
Replace the following line:
$f3->write( $imageName, $img->dump() );
with:
$f3->write( $imageName, $img->dump('jpeg',null,50) );
The 50 in the above line of code is the image quality. Reduce it to make the images load faster. Use 100 for full quality.
Remember that this will only take effect on new images uploaded to the server, since images are resized on upload.