(PECL ps:1.1.0-1.1.1)
ps_setgray — Sets gray value
Sets the gray value for all following drawing operations.
Resource identifier of the postscript file as returned by ps_new().
The value must be between 0 (white) and 1 (black).
성공할 경우 TRUE를, 실패할 경우 FALSE를 반환합니다.