Remove header image filter

I’m not sure what you mean — do you want to change the size of the header image? If so, you can do so following the instructions in this thread:
http://ww.wp.xz.cn/support/topic/make-header-larger?replies=3

If you want to adjust the opacity of the header image, you can do so following the instructions in this thread:
http://ww.wp.xz.cn/support/topic/how-to-remove-transparency-from-headertagline-and-menu-and-circles?replies=4

Fantastic, glad I could help!