PHP sharpness convolution martix

[Gizmis]

I'm using a convolution matrix for sharpness in PHP GD and I want to change the sharpness "level". Where would I make changes to this if I want to make it more or less sharp?\[code\]$image = imagecreatefromjpeg('pic.jpg');$matrix = array( array(0, -1, 0), array(-1, 5, -1), array(0, -1, 0));imageconvolution($image, $matrix, 1, 0.001);header("Content-type: image/jpeg");imagejpeg($image);\[/code\]