Imagick::setImageAlphaChannel

(PECL imagick 2 >= 2.1.0, PECL imagick 3)

Imagick::setImageAlphaChannel — Sets image alpha channel

说明

public Imagick::setImageAlphaChannel(int $mode): bool

Activate or deactivate image alpha channel. The mode is one of the Imagick::ALPHACHANNEL_* constants. 此方法在Imagick基于ImageMagick 6.3.8以上版本编译时可用。

参数

mode: One of the Imagick::ALPHACHANNEL_* constants

返回值

成功时返回 true。

错误／异常

错误时抛出 ImagickException。

参见

Imagick::setImageMatte() - Sets the image matte channel
Imagick Alpha Channel Constants

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User Contributed Notes 1 note

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simonjjarrett at gmail dot com ¶

3 years ago

If you're having trouble with white backgrounds turning black when converting PDFs to other formats, you need to use this function with Imagick::ALPHACHANNEL_REMOVE as the parameter (this is not currently on the constants page, but it exists in PHP 7.2) to remove the alpha channel.

<?php
$im->setImageAlphaChannel(Imagick::ALPHACHANNEL_REMOVE );
?>

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