Copy a part of src_im
onto dst_im starting at the
x,y coordinates src_x, src_y with a width of src_w and a height of src_h. The portion defined will
be copied onto the x,y coordinates,
dst_x and dst_y.
The two images will be merged according to pct which can range from 0 to 100.
When pct = 0, no action is
taken, when 100 this function behaves identically to
imagecopy().
注: This function was added in PHP 4.0.6