为什么在实际处理当中，下面的代码值移除了白色，请教是怎么回事？

Question

把一张图片（根据指定的RGB颜色范围）透明化。

$o_pic = '1.jpg';//要处理的色阶起始值$begin_r = 215;$begin_g = 215;$begin_b = 215;

list($src_w,$src_h,$src_type) = getimagesize($o_pic);// 获取原图像信息$file_ext = get_ext($o_pic);//获取扩展名$target_im = imagecreatetruecolor($src_w,$src_h);//新图if($file_ext == 'jpg') //转换JPG 开始
{    $src_im = ImageCreateFromJPEG($o_pic);
      
    imagecopymerge($target_im,$src_im,0,0,0,0,$src_w,$src_h,100);    for($x = 0; $x < $src_w; $x++)
    {        for($y = 0; $y < $src_h; $y++)
        {            $rgb = imagecolorat($src_im, $x, $y);            $r = ($rgb >> 16) & 0xFF;            $g = ($rgb >> 8) & 0xFF;            $b = $rgb & 0xFF;            if($r > $begin_r && $g > $begin_g && $b > $begin_b ){   
                imagecolortransparent($target_im, imagecolorallocate($target_im,$r, $g, $b));                
            }
        }
    }

}

Answer 1

/**&nbsp;* Created by PhpStorm.&nbsp;* User: shellus&nbsp;* Date: 2016-12-01&nbsp;* Time: 23:12&nbsp;*/require 'vendor/autoload.php';// import the Intervention Image Manager Classuse Intervention\Image\ImageManager;// create an image manager instance with favored driver$manager = new ImageManager(array('driver' => 'gd'));$img = &nbsp;$manager->make('1.jpg');for ($y = 0; $y < $img->height(); $y++){&nbsp; &nbsp; for ($x = 0; $x < $img->width(); $x++)&nbsp; &nbsp; {&nbsp; &nbsp; &nbsp; &nbsp; $c = $img -> pickColor($x, $y, 'array');&nbsp; &nbsp; &nbsp; &nbsp; if(abs($c[0] - 205) < 50 &nbsp;&& abs($c[1] - 223) < 50 && abs($c[2] - 211) < 50 ){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $c[0] = $c[1] = $c[2] = 255;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; $img -> pixel($c, $x, $y);&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }}$img -> save();

Answer 2

请不要用jpg,因为jpg不支持透明所以变白了,用imagecreatetruecolor或是imagecreatefrompng