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);
?>
Imagick::evaluateImage
(PECL imagick 2.0.0)
Imagick::evaluateImage — Applies an expression to an image
Descrizione
Imagick::evaluateImage
( int
$op
, float $constant
[, int $channel = Imagick::CHANNEL_DEFAULT
] ) : boolApplys 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.
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;
?>
Valori restituiti
Restituisce TRUE in caso di successo.
Errori/Eccezioni
Lancia una ImagickException in caso di errore.
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User Contributed Notes 1 note
nils dot rocine at gmail dot com ¶
7 years ago
