(PECL imagick 2, PECL imagick 3)
Imagick::previewImages — Quickly pin-point appropriate parameters for image processing
$preview
) : boolTiles 9 thumbnails of the specified image with an image processing operation applied at varying strengths. This is helpful to quickly pin-point an appropriate parameter for an image processing operation.
成功时返回 true。
错误时抛出 ImagickException。