Convert ICO to PNG using PHP Imagick

I am currently trying to convert an ICO file to a 16×16 px PNG, using PHP-Imagick. What I’ve tried so far:

<?php
if (empty(Imagick::queryFormats("ICO"))) {
    throw new Exception('Unsupported format');
}

$sourceFile = __DIR__ . '/favicon.ico';
$targetFile = __DIR__ . '/favicon.png';

$im = new Imagick($sourceFile);
$im->writeImages($targetFile, true);

This works partially. The problem is, that an ICO file may contain multiple images, so the code above creates multiple PNG files

favicon-0.png
favicon-1.png
…

for every size. This is okay, but then, I need the possibility to find the one that is close to 16×16 px, scale it down (if needed) and delete all others. For this, I already tried some things and this is where I’m stuck currently:

<?php
if (empty(Imagick::queryFormats("ICO"))) {
    throw new Exception('Unsupported format');
}

$sourceFile = __DIR__ . '/favicon.ico';
$targetFile = __DIR__ . '/favicon.png';

$im = new Imagick($sourceFile);
$count = $im->getNumberImages();

if ($count > 1) {
    for ($x = 1; $x <= $count; $x++) {
        $im->previousImage();

        $tmpImageWidth = $im->getImageWidth();
        $tmpImageHeight = $im->getImageHeight();

        // ???
    }
}

$im->writeImages($targetFile, true);

I guess, i would find a working way with some trial and error. But I would like to know, if there’s an easier way to achieve this.

TL;DR: I need a simple way to convert an ICO file of any size to a 16×16 px PNG, using PHP-Imagick (using GD isn’t an option).

Update:

My (currently working but maybe suboptimal) solution:

<?php
if (empty(Imagick::queryFormats("ICO"))) {
    throw new Exception('Unsupported format');
}

$sourceFile = __DIR__ . '/favicon.ico';
$targetFile = __DIR__ . '/favicon.png';

$im = new Imagick($sourceFile);
$count = $im->getNumberImages();
$targetWidth = $targetHeight = 16;

if ($count > 1) {
    $images = [];

    for ($x = 1; $x <= $count; $x++) {
        $im->previousImage();

        $images[] = [
            'object' => $im,
            'size' => $im->getImageWidth() + $im->getImageHeight()
        ];
    }

    $minSize = min(array_column($images, 'size'));
    $image = array_values(array_filter($images, function($image) use ($minSize) {
        return $minSize === $image['size'];
    }))[0];

    $im = $image['object'];

    if ($image['size'] <> $targetWidth + $targetHeight) {
        $im->cropThumbnailImage($targetWidth, $targetHeight);
    }
}
else {
    if ($im->getImageWidth() <> $targetWidth || $im->getImageHeight() <> $targetHeight) {
        $im->cropThumbnailImage($targetWidth, $targetHeight);
    }
}

$im->writeImage($targetFile);

Answer

My final solution:

<?php
if (empty(Imagick::queryFormats("ICO"))) {
    throw new Exception('Unsupported format');
}

$sourceFile = __DIR__ . '/favicon.ico';
$targetFile = __DIR__ . '/favicon.png';

$im = new Imagick($sourceFile);
$count = $im->getNumberImages();
$targetWidth = $targetHeight = 16;

if ($count > 1) {
    $images = [];

    for ($x = 1; $x <= $count; $x++) {
        $im->previousImage();

        $images[] = [
            'object' => $im,
            'size' => $im->getImageWidth() + $im->getImageHeight()
        ];
    }

    $minSize = min(array_column($images, 'size'));
    $image = array_values(array_filter($images, function($image) use ($minSize) {
        return $minSize === $image['size'];
    }))[0];

    $im = $image['object'];

    if ($image['size'] <> $targetWidth + $targetHeight) {
        $im->cropThumbnailImage($targetWidth, $targetHeight);
    }
}
else {
    if ($im->getImageWidth() <> $targetWidth || $im->getImageHeight() <> $targetHeight) {
        $im->cropThumbnailImage($targetWidth, $targetHeight);
    }
}

$im->writeImage($targetFile);

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Answer