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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