php的图片等比缩放

<?php
function resizeImage($sourceImage, $destinationImage, $width, $height) {
    // 获取原始图片信息
    list($sourceWidth, $sourceHeight, $sourceType) = getimagesize($sourceImage);

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

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

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

    // 开始缩放
    imagecopyresampled($destinationResource, $sourceResource, 0, 0, 0, 0, $newWidth, $newHeight, $sourceWidth, $sourceHeight);

    // 根据目标图片类型保存图像
    switch ($sourceType) {
        case IMAGETYPE_GIF:
            imagegif($destinationResource, $destinationImage);
            break;
        case IMAGETYPE_JPEG:
            imagejpeg($destinationResource, $destinationImage);
            break;
        case IMAGETYPE_PNG:
            imagepng($destinationResource, $destinationImage);
            break;
    }

    // 释放内存
    imagedestroy($sourceResource);
    imagedestroy($destinationResource);

    return true;
}

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

resizeImage($sourceImage, $destinationImage, $width, $height);
?>

imagejpeg($destinationResource, $destinationImage, 90); // 90表示质量为90%