magento_get_all_unused_product_images.php

<?php

$mediaDir = Mage::getBaseDir('media');
$varDir = Mage::getBaseDir('var');
$backupDir = "$varDir/media_unused";

if (!is_dir($backupDir)) {
    mkdir($backupDir, 0770, true);
}

$productsImagesDir = "$mediaDir/catalog/product";

$validPaths = array_merge(['-'], range(0, 9));
for ($i = 'a'; $i < 'z'; $i++) {
    $validPaths[] = $i;
}
$validPaths[] = 'z';

$imagesInDatabase = [];
$sql = 'SELECT * FROM catalog_product_entity_media_gallery';
$connection = Mage::getSingleton('core/resource')->getConnection('core_read');
foreach ($connection->fetchAll($sql) as $row) {
    $imagesInDatabase[] = $row['value'];
}

$pathsLevel1 = array_intersect($validPaths, scandir($productsImagesDir));

foreach ($pathsLevel1 as $pathLevel1) {
    $pathsLevel2 = array_intersect($validPaths, scandir("$productsImagesDir/$pathLevel1"));

    foreach ($pathsLevel2 as $pathLevel2) {
        $imagesAbsolutePath = "$productsImagesDir/$pathLevel1/$pathLevel2";
        $images = array_diff(scandir($imagesAbsolutePath), ['.', '..']);

        if (!count($images)) {
            continue;
        }

        foreach ($images as $image) {
            $imageFilePath = "/$pathLevel1/$pathLevel2/$image";

            if (in_array($imageFilePath, $imagesInDatabase)) {
                continue;
            }

            $currentBackupDir = "$backupDir/$pathLevel1/$pathLevel2";

            if (!is_dir($currentBackupDir)) {
                mkdir($currentBackupDir, 0770, true);
            }

            rename("$imagesAbsolutePath/$image", "$currentBackupDir/$image");
        }
    }
}