使用Imagick和PHP删除空格，然后另存为透明PNG

Question

I've got an image and want to remove all whitespace around it, and then save it as a transparent PNG. I'm using Imagick in PHP to do so, but my script doesn't seem to function properly.

<?php
$im = new Imagick("http://images.icecat.biz/img/norm/high/14688888-2862.jpg");

$im->borderImage("#ffffff", 20, 20);
$im->trimImage(0.3);

$im->setImagePage($im->getImageWidth(), $im->getImageHeight(), 0, 0);
$im->setImageFormat("png");

header("Content-Type: image/" . $im->getImageFormat());
echo $im->getImageBlob();
?>

What do I need to do to remove all white (and close to white) areas at the borders? And when that is done, can I easily resize the image to crop all of the transparency?

Answer 1

The fuzz factor needs to be a quantum scaled value, not just for this function but almost all functions that take 'fuzz' as a parameter.

ie you need to scale it up to the quantum range.

$im->trimImage(0.3 * \Imagick::getQuantum());

Or if you are using an earlier version of Imagick that doesn't have that method, then instead do:

$range = $image->getQuantumRange();
$image->trimImage(0.3 * $range['quantumRangeLong']);

The reason for this is to allow precise control over the pixel matching. If the value was passed in as a float value in the range 0-1 it would not possible to have exact control over the value that was used for matching.

By instead using an integer value (for versions of Imagick that do not have HDRI enabled) it allows you to precisely control the values that are compared for the operation.

Answer 2

You need something like an autocrop based on pixel values, I think this will help: http://www.imagemagick.org/script/command-line-options.php#trim

you might also like: http://fmwconcepts.com/imagemagick/autotrim/index.php

source: http://www.imagemagick.org/discourse-server/viewtopic.php?t=10843