Responsive Header Image Only Showing Center

So I have been trying to figure this out but I can’t seem to get anywhere.

I’m working with a premium responsive theme. It works well but there is one specific fix I’m trying to implement.

I need the header image to show only the left side of the image when it is viewed on a tablet or phone; and right now it shows the center.

Below is the code that I’m pretty positive controls all the header responsiveness.

}
img.size-full,
img.size-large,
img.header-image,
img.wp-post-image {
height: auto; /* Make sure images with WordPress-added height and width attributes are scaled correctly */
}

Is there a way to make the image show only the left side either by coding or a plugin?

Thanks in advance.