imagecreatefromgif()函数的PHP手册页上有简短的代码片段，应该是您所需要的:

There is a brief snippet of code in the PHP manual page of the imagecreatefromgif() function that should be what you need:

imagecreatefromgif评论#59787，由ZeBadger

imagecreatefromgif comment #59787 by ZeBadger