php等比压缩图片

<?php
function compress_image($source, $destination, $quality) {
    $info = getimagesize($source);

    if ($info['mime'] == 'image/jpeg') {
        $image = imagecreatefromjpeg($source);
    } elseif ($info['mime'] == 'image/gif') {
        $image = imagecreatefromgif($source);
    } elseif ($info['mime'] == 'image/png') {
        $image = imagecreatefrompng($source);
    }

    $width = imagesx($image);
    $height = imagesy($image);

    // 计算等比压缩后的宽度和高度
    $new_width = 800; // 可以根据需要调整
    $new_height = round($height * ($new_width / $width));

    $new_image = imagecreatetruecolor($new_width, $new_height);
    imagecopyresampled($new_image, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);

    if (imageresolution($new_image) != 72) {
        imageresolution($new_image, 72);
    }

    if ($info['mime'] == 'image/jpeg') {
        imagejpeg($new_image, $destination, $quality);
    } elseif ($info['mime'] == 'image/gif') {
        imagegif($new_image, $destination);
    } elseif ($info['mime'] == 'image/png') {
        imagepng($new_image, $destination, 9 - ($quality / 10));
    }

    imagedestroy($image);
    imagedestroy($new_image);
}

$source = 'path/to/source/image.jpg';
$destination = 'path/to/destination/image.jpg';
$quality = 75; // 质量范围为0-100

compress_image($source, $destination, $quality);
?>