This patch allows you to use IMAGE_WIDTH and IMAGE_HEIGHT constants to define the width and height of the image that is output.
Please take note that once set, the size cannot be changed. This means if you are batch processing images they will all have to be the same size unless you split your batch processing by desired size.
Also note, while I gave a width and height option, I strongly advise against setting them differently. QR Codes will probably not display correctly if this is done.
Patch to qrimage.php for fixed width / height images.
lib missing some sizing features, currently it is possible only to specify pixel size multiplier, and whole image size is function of it, but also of qr code size and required silent zone.
Maybe it will be needed for future release to allow specifying size and calculating resulting pixel size and silent zone from it.