Separates a channel from the image

# Imagick::separateImageChannel

(PECL imagick 2, PECL imagick 3)

Imagick::separateImageChannel — Separates a channel from the image

### 说明

public function Imagick::separateImageChannel(int `$channel`): bool

Separates a channel from the image and returns a grayscale image. A channel is a particular color component of each pixel in the image.

### 参数

`channel`

  Which 'channel' to return. For colorspaces other than RGB, you can still use the CHANNEL_RED, CHANNEL_GREEN, CHANNEL_BLUE constants to indicate the 1st, 2nd and 3rd channels.

### 返回值

成功时返回 `true`。

### 错误／异常

错误时抛出 ImagickException。

### 示例

示例 #1 Imagick::separateImageChannel()

    <?php
    function separateImageChannel($imagePath, $channel) {
        $imagick = new \Imagick(realpath($imagePath));
        $imagick->separateimagechannel($channel);
        header("Content-Type: image/jpg");
        echo $imagick->getImageBlob();
    }

    separateImageChannel($imagePath, \Imagick::CHANNEL_GREEN);

    ?>

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