php图片按比例缩放

<?php
function resizeImage($source, $destination, $width, $height) {
    // 获取原始图片尺寸
    list($sourceWidth, $sourceHeight, $sourceType) = getimagesize($source);

    // 根据图片类型创建图像资源
    switch ($sourceType) {
        case IMAGETYPE_GIF:
            $sourceImage = imagecreatefromgif($source);
            break;
        case IMAGETYPE_JPEG:
            $sourceImage = imagecreatefromjpeg($source);
            break;
        case IMAGETYPE_PNG:
            $sourceImage = imagecreatefrompng($source);
            break;
        default:
            return false;
    }

    // 计算缩放后的尺寸
    if ($sourceWidth > $sourceHeight) {
        $newWidth = $width;
        $newHeight = intval($sourceHeight * $width / $sourceWidth);
    } else {
        $newHeight = $height;
        $newWidth = intval($sourceWidth * $height / $sourceHeight);
    }

    // 创建目标图像资源
    $destinationImage = imagecreatetruecolor($newWidth, $newHeight);

    // 按比例缩放图片
    imagecopyresampled($destinationImage, $sourceImage, 0, 0, 0, 0, $newWidth, $newHeight, $sourceWidth, $sourceHeight);

    // 保存缩放后的图片
    switch ($sourceType) {
        case IMAGETYPE_GIF:
            imagegif($destinationImage, $destination);
            break;
        case IMAGETYPE_JPEG:
            imagejpeg($destinationImage, $destination);
            break;
        case IMAGETYPE_PNG:
            imagepng($destinationImage, $destination);
            break;
    }

    // 销毁图像资源
    imagedestroy($sourceImage);
    imagedestroy($destinationImage);

    return true;
}

// 使用示例
$source = 'path/to/source/image.jpg';
$destination = 'path/to/destination/image.jpg';
$width = 300;
$height = 200;

resizeImage($source, $destination, $width, $height);
?>