php等比例缩放图片

<?php
function resizeImage($source, $destination, $newWidth, $quality = 90) {
    // 获取原始图片的尺寸和类型
    list($width, $height, $type) = getimagesize($source);
    
    // 根据图片类型创建图像资源
    switch ($type) {
        case IMAGETYPE_JPEG:
            $image = imagecreatefromjpeg($source);
            break;
        case IMAGETYPE_PNG:
            $image = imagecreatefrompng($source);
            break;
        case IMAGETYPE_GIF:
            $image = imagecreatefromgif($source);
            break;
        default:
            return false;
    }
    
    // 计算新的高度以保持等比例缩放
    $newHeight = ($height / $width) * $newWidth;
    
    // 创建一个新的图像资源
    $newImage = imagecreatetruecolor($newWidth, $newHeight);
    
    // 保持图片质量
    imagecopyresampled($newImage, $image, 0, 0, 0, 0, $newWidth, $newHeight, $width, $height);
    
    // 根据图片类型保存新的图像
    switch ($type) {
        case IMAGETYPE_JPEG:
            imagejpeg($newImage, $destination, $quality);
            break;
        case IMAGETYPE_PNG:
            imagepng($newImage, $destination, 9);
            break;
        case IMAGETYPE_GIF:
            imagegif($newImage, $destination);
            break;
    }
    
    // 销毁图像资源
    imagedestroy($image);
    imagedestroy($newImage);
    
    return true;
}

// 使用示例
$source = 'path/to/source/image.jpg';
$destination = 'path/to/destination/image_resized.jpg';
$newWidth = 300;

resizeImage($source, $destination, $newWidth);
?>