This function seems to do the same thing as photoshop feture convas size, you set size of convas and position of your image's top left corner (x,y) inside that convas.
(PECL imagick 2 >= 2.3.0, PECL imagick 3)
Imagick::resetImagePage — Reset image page
The page definition as a string. The string is in format WxH+x+y. 此方法在Imagick基于ImageMagick 6.3.6以上版本编译时可用。
page
The page definition. For example 7168x5147+0+0
成功时返回 true。