固定图片裁剪的宽高，裁剪不变形方法整理

图片裁剪类

class ImageForm
{
    private $file;    //图片地址
    private $width;   //图片宽度
    private $height;   //图片高度
    private $type;    //图片类型
    private $img;    //原图的资源句柄
    private $new;    //新图的资源句柄

    //构造方法，初始化
    public function __construct($_file)
    {
        $this->file = $_file;
        list($this->width, $this->height, $this->type) = getimagesize($this->file);
        $this->img = $this->getFromImg($this->file, $this->type);
    }

    //缩略图(固定长高容器，图像等比例，扩容填充，裁剪)[固定了大小，不失真，不变形]
    public function crop($path, $fileName,$new_width = 0, $new_height = 0)
    {
        if (empty($new_width) && empty($new_height)) {
            $new_width = $this->width;
            $new_height = $this->height;
        }

        if (!is_numeric($new_width) || !is_numeric($new_height)) {
            $new_width = $this->width;
            $new_height = $this->height;
        }

        //创建一个容器
        $_n_w = $new_width;
        $_n_h = $new_height;

        //创建裁剪点
        $_cut_width = 0;
        $_cut_height = 0;

        if ($this->width < $this->height) {
            $new_width = ($new_height / $this->height) * $this->width;
        } else {
            $new_height = ($new_width / $this->width) * $this->height;
        }


        if ($new_width < $_n_w) { //如果新高度小于新容器高度
            $r = $_n_w / $new_width; //按长度求出等比例因子
            $new_width *= $r; //扩展填充后的长度
            $new_height *= $r; //扩展填充后的高度
            $_cut_height = ($new_height - $_n_h) / 2; //求出裁剪点的高度
        }

        if ($new_height < $_n_h) { //如果新高度小于容器高度
            $r = $_n_h / $new_height; //按高度求出等比例因子
            $new_width *= $r; //扩展填充后的长度
            $new_height *= $r; //扩展填充后的高度
            $_cut_width = ($new_width - $_n_w) / 2; //求出裁剪点的长度
        }

        $this->new = imagecreatetruecolor($_n_w, $_n_h);

        imagecopyresampled($this->new, $this->img, 0, 0, $_cut_width, $_cut_height, $new_width, $new_height, $this->width, $this->height);
        $saveCrop = str_replace('original', 'crop', $path);
        $uploadPath = \Yii::getAlias('@uploadPath/' . $saveCrop);
        FileHelper::createDirectory($uploadPath);
        imagejpeg($this->new, $uploadPath . DIRECTORY_SEPARATOR . $fileName);
    }

    //加载图片，各种类型，返回图片的资源句柄
    private function getFromImg($_file, $_type)
    {
        switch ($_type) {
            case 1 :
                $img = imagecreatefromgif($_file);
                break;
            case 2 :
                $img = imagecreatefromjpeg($_file);
                break;
            case 3 :
                $img = imagecreatefrompng($_file);
                break;
            default:
                break;
        }
        return $img;
    }
    //图像输出
    public function out()
    {
        imagepng($this->new, $this->file);
        imagedestroy($this->img);
        imagedestroy($this->new);
    }
}

裁剪方法调用举例

这里举例生成固定宽高为750*750的尺寸

 $image_thumb = new ImageForm('/20200805/original/1596613040.jpg');
 $image_thumb->crop($saveOriginPath, $imginfo,750,750);

参考网站：https://www.cnblogs.com/lanxiaoyu/p/5361950.html