php GD 圆图 -处理成圆图片

 <?php
  /**
  * 处理成圆图片,如果图片不是正方形就取最小边的圆半径,从左边开始剪切成圆形
  * @param  string $imgpath [description]
  * @return [type]          [description]
  */
     function yuan_img($imgpath = './code_png/share.jpg') {
         $ext     = pathinfo($imgpath);
         $src_img = null;
         switch ($ext['extension']) {
             case 'jpg':
                 $src_img = imagecreatefromjpeg($imgpath);
                 break;
             case 'png':
                 $src_img = imagecreatefrompng($imgpath);
                 break;
         }
         $wh  = getimagesize($imgpath);
         $w   = $wh[0];
         $h   = $wh[1];
         $w   = min($w, $h);
         $h   = $w;
         $img = imagecreatetruecolor($w, $h);
         //这一句一定要有
         imagesavealpha($img, true);
         //拾取一个完全透明的颜色,最后一个参数127为全透明
         $bg = imagecolorallocatealpha($img, 255, 255, 255, 127);
         imagefill($img, 0, 0, $bg);
         $r   = $w / 2; //圆半径
         $y_x = $r; //圆心X坐标
         $y_y = $r; //圆心Y坐标
         for ($x = 0; $x < $w; $x++) {
             for ($y = 0; $y < $h; $y++) {
                 $rgbColor = imagecolorat($src_img, $x, $y);
                 if (((($x - $r) * ($x - $r) + ($y - $r) * ($y - $r)) < ($r * $r))) {
                     imagesetpixel($img, $x, $y, $rgbColor);
                 }
             }
         }

         return $img;
 }

 Header("Content-Type: image/png");
   $img = yuan_img();

 imagepng($img);

46 imagedestroy($img);

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