How to make QR code transparent in php

Directly make the background of the QR code image transparent (Recommended learning: PHP video tutorial)

//二维码内容
		$qrcodeContent = '此处存链接的话，参数不宜过长，否则导致生成二维码时间太长！！！';
		//容错级别
		$errorCorrectionLevel = 'L';
		//生成图片大小
		$matrixPointSize = 6;
		//生成二维码图片
		\QRcode::png($qrcodeContent, 'qrcode.png', $errorCorrectionLevel, $matrixPointSize, 2);
		$QR = 'qrcode.png';//已经生成的原始二维码图
		//将二维码背景变透明
		$resource = imagecreatefrompng($QR);
		@unlink($QR);
		$bgcolor = imagecolorallocate($resource, 255, 255, 255);
		imagefill($resource, 0, 0, $bgcolor);
		imagecolortransparent($resource, $bgcolor);
		imagepng($resource,'qrcode_copy.png');	/*先处理成透明图再进行缩放就不会出现白黑点情况了！！！（至少效果好多了，而先进行缩放再处理背景透明就会出现很多白黑点！）*/
		@imagedestroy($resource);
                //获取对应游戏海报二维码位置
                $qrcode_pos = $pos;//$pos = [x,y]
                //获取对应游戏海报二维码规格
                $qrcode_spec = $spec;//$spec = [w,h]
                $resource = smart_resize_image('qrcode_copy.png', $qrcode_spec[0], $qrcode_spec[1], true);
                imagepng($resource,'qrcode_'.$gameType.'.png');//存储改变大小后的透明二维码
                $qrcode = 'qrcode_'.$gameType.'.png';
                //将透明背景的二维码贴到海报图指定位置
                $poster_with_qrcode_or_invitedcode_url = waterImage($posterUrl, $qrcode, $qrcode_pos[0], $qrcode_pos[1]);
                @imagedestroy($resource);
                @unlink('qrcode_copy.png');
                @unlink($qrcode);

The above calling method is as follows:

/**
     * 调整图片大小并返回图片资源
     * @param $file
     * @param int $width
     * @param int $height
     * @param bool $proportional
     * @return bool|resource
     * @author zsb
     */
    function smart_resize_image($file, $width = 0, $height = 0, $proportional = false)
    {
        if ( $height <= 0 && $width <= 0 ) {
            return false;
        }
        $info = getimagesize($file);
        $image = '';
        $final_width = 0;
        $final_height = 0;
        list($width_old, $height_old) = $info;
        if ($proportional) {
            if ($width == 0) {
                $factor = $height/$height_old;
            }elseif ($height == 0) {
                $factor = $width/$width_old;
            }else {
                $factor = min ( $width / $width_old, $height / $height_old);
            }
            $final_width = round ($width_old * $factor);
            $final_height = round ($height_old * $factor);
        }else {
            $final_width = ( $width <= 0 ) ? $width_old : $width;
            $final_height = ( $height <= 0 ) ? $height_old : $height;
        }
        switch ($info[2]) {
            case IMAGETYPE_GIF:
                $image = imagecreatefromgif($file);
                break;
            case IMAGETYPE_JPEG:
                $image = imagecreatefromjpeg($file);
                break;
            case IMAGETYPE_PNG:
                $image = imagecreatefrompng($file);
                break;
            default:
                return false;
        }
        $image_resized = imagecreatetruecolor( $final_width, $final_height );
        if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
            $trnprt_indx = imagecolortransparent($image);
            // If we have a specific transparent color
            if ($trnprt_indx >= 0) {
                // Get the original image's transparent color's RGB values
                $trnprt_color  = imagecolorsforindex($image, $trnprt_indx);
                // Allocate the same color in the new image resource
                $trnprt_indx  = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $trnprt_indx);
                // Set the background color for new image to transparent
                imagecolortransparent($image_resized, $trnprt_indx);
            }
            // Always make a transparent background color for PNGs that don't have one allocated already
            elseif ($info[2] == IMAGETYPE_PNG) {
                // Turn off transparency blending (temporarily)
                imagealphablending($image_resized, false);
                // Create a new transparent color for image
                $color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $color);
                // Restore transparency blending
                imagesavealpha($image_resized, true);
            }
        }
 
        imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
 
        return $image_resized;
    }
 
    /**
     * 获取图片信息
     * @param $filename 传过来的参数是文件名字符串
     * @return mixed 返回值是一个数组，包含图片宽度、高度、创建和输出的字符串以及扩展名
     *  @author zsb
     */
    function getImageInfo($filename){
        if(@!$info = getimagesize($filename)){//getimagesize()函数可以得到文件信息,
            //还可以判断图片是否为真实的图片类型，详细功能见PHP手册
            exit('文件不是真实图片');
        }
        $fileInfo['width'] = $info[0];
        $fileInfo['height'] = $info[1];
        $mime = image_type_to_mime_type($info[2]);//info[2]这个是图片类型对应的数字，此函数可以根据该数字返回出文件对应的MIME类型，详细见手册
        $createFun = str_replace('/', 'createfrom', $mime);//将$mime中的'/'替换成'createfrom'，
        //因为后边要用到imagecreatefromjpeg/jpg/png 这个函数，这样就可以动态使用不同的函数了
        $outFun = str_replace('/', '', $mime);
        $fileInfo['createFun'] = $createFun;
        $fileInfo['outFun'] = $outFun;
        $fileInfo['ext'] = strtolower(image_type_to_extension($info[2]));//image_type_to_extension()是得到文件后缀名函数
        return $fileInfo;//返回文件信息
    }
 
    /**
     * 给图片加水印并返回新图片地址
     * @param $dstName
     * @param $srcName
     * @param int $x 图片水印的位置  (0,0)代表左上角
     * @param int $y 图片水印的位置  (0,0)代表左上角
     * @param string $dest 默认保存的位置
     * @param string $pre  默认文件名前缀
     * @param int $pct  图片水印的透明度
     * @return string
     * @author zsb
     */
    function waterImage($dstName, $srcName, $x = 0, $y = 0, $dest = 'images/waterImage', $pre = 'waterImage_', $pct = 100){
        //获取图片信息
        $dstInfo = getImageInfo($dstName);
        $srcInfo = getImageInfo($srcName);
        //创建画布
        $dst_im = $dstInfo['createFun']($dstName);
        $src_im = $srcInfo['createFun']($srcName);
        $src_width = $srcInfo['width'];
        $src_height = $srcInfo['height'];
        $dst_width = $dstInfo['width'];
        $dst_height = $dstInfo['height'];
 
        imagecopymerge($dst_im, $src_im, $x, $y, 0, 0, $src_width, $src_height, $pct);
 
        if($dest && !file_exists($dest)){
            mkdir($dest,0777,true);
        }
 
        //$randNum = mt_rand(100000,999999);
        $dstName = "$pre".$dstInfo['ext'];
        $destination = $dest ? $dest.'/'.$dstName : $dstName;
        $dstInfo['outFun']($dst_im,$destination);
        imagedestroy($src_im);
        imagedestroy($dst_im);
        return $destination;
    }

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