PHP实现图片指定宽高缩放的两种方法

<?php
// 指定图片路径
$image_path = 'path/to/your/image.jpg';
 
// 指定缩放后的宽度和高度
$new_width = 200;
$new_height = 150;
 
// 获取图片信息
list($width, $height, $type) = getimagesize($image_path);
 
// 根据图片类型创建图片资源
switch ($type) {
    case IMAGETYPE_JPEG:
        $image = imagecreatefromjpeg($image_path);
        break;
    case IMAGETYPE_PNG:
        $image = imagecreatefrompng($image_path);
        break;
    case IMAGETYPE_GIF:
        $image = imagecreatefromgif($image_path);
        break;
    default:
        die('Unsupported image type');
}
 
// 创建一个新的空白图像
$new_image = imagecreatetruecolor($new_width, $new_height);
 
// 保持 PNG 和 GIF 图像的透明度
if ($type == IMAGETYPE_PNG || $type == IMAGETYPE_GIF) {
    imagealphablending($new_image, false);
    imagesavealpha($new_image, true);
    $transparent = imagecolorallocatealpha($new_image, 255, 255, 255, 127);
    imagefilledrectangle($new_image, 0, 0, $new_width, $new_height, $transparent);
}
 
// 将原图像复制到新图像并进行缩放
imagecopyresampled($new_image, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
 
// 输出新图像
header('Content-Type: image/' . image_type_to_extension($type, false));
// 将新图像保存到目标路径
$target_path = 'path/to/your/image_100_150.png';
imagepng($new_image, $target_path);
 
// 释放内存
imagedestroy($image);
imagedestroy($new_image);
?>

$image = \think\Image::open('./image.png');
// 按照原图的比例生成一个最大为150*150的缩略图并保存为thumb.png
$image->thumb(150, 150)->save('./thumb.png');