Preg-replace file name

I use this fonction:

`<?php function k99_attachment_image_link_void( $content ) {
$content =
preg_replace(array(‘{<a[^>]*><img}’,'{ />}’), array(‘<img’,’/>’), $content);

return $content;
}

add_filter( ‘the_content’, ‘k99_attachment_image_link_void’ );

?>’

This function remove the link of my images.

My images are called like this:

imagesname_188x145.jpg

How to change the width and the height (actyaly 188×145) of the image in this function (the width and the height that I want is 300×231).

Thanks