Imagick::evaluateImage

(PECL imagick 2, PECL imagick 3)

Imagick::evaluateImage — Applies an expression to an image

Descrizione

public function Imagick::evaluateImage(int $op, float $constant, int $channel = Imagick::CHANNEL_DEFAULT): bool

Applies an arithmetic, relational, or logical expression to an image. Use these operators to lighten or darken an image, to increase or decrease contrast in an image, or to produce the "negative" of an image.

Elenco dei parametri

op: The evaluation operator
constant: The value of the operator
channel: Provide any channel constant that is valid for your channel mode. To apply to more than one channel, combine channeltype constants using bitwise operators. Refer to this list of channel constants.

Valori restituiti

Restituisce true in caso di successo.

Errori/Eccezioni

Lancia una ImagickException in caso di errore.

Esempi

Example #1 Using Imagick::evaluateImage()

Using evaluateImage to reduce opacity in an image.

<?php
// Create new object with the image
$im = new Imagick('example-alpha.png');

// Reduce the alpha by 50%
$im->evaluateImage(Imagick::EVALUATE_DIVIDE, 2, Imagick::CHANNEL_ALPHA);

// Output the image
header("Content-Type: image/png");
echo $im;
?>

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User Contributed Notes 1 note

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nils dot rocine at gmail dot com ¶

14 years ago

What worked for me to convert a JPG source file to a semi-transparent PNG.

<?php
    $srcImagick = new Imagick($srcPath);
    
    $pathTo50Perc = 'transparent1.png';
    
    $srcImagick->setImageAlphaChannel(Imagick::ALPHACHANNEL_OPAQUE);
    
    $srcImagick->evaluateImage(Imagick::EVALUATE_DIVIDE, 2, Imagick::CHANNEL_ALPHA);

    $srcImagick->writeImage($pathTo50Perc);
?>

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