imagecopyresampled问题 - 黑色边框右下角...

Question

第一个选项有效，第二个选项没有......我不明白为什么？我拍摄1500×1500像素的图像，如果它通过第一个选项，结果是正确的，如果它通过第二个，我在右边和底部得到一个黑色边框......

if ($this_imagesize[0] > 1000)
    {
        $thumb_source = imagecreatefromjpeg('/path/' . $this_image_id . '.jpg');

        $thumbnail = imagecreatetruecolor(1000, intval(1000 * ($this_imagesize[1] / $this_imagesize[0])));

        imagefill($thumbnail, 0, 0, imagecolorallocate($tn, 255, 255, 255));

        imagecopyresampled($thumbnail, $thumb_source, 0, 0, 0, 0, 1000, intval(1000 * ($this_imagesize[1] / $this_imagesize[0])), $this_imagesize[0], $this_imagesize[1]);

        unlink('/path/' . $this_image_id . '.jpg');

        imagejpeg($thumbnail, '/path/' . $this_image_id . '.jpg', 75);
    }

if ($this_imagesize[1] > 1000)
    {
        $thumb_source = imagecreatefromjpeg('/path/' . $this_image_id . '.jpg');

        $thumbnail = imagecreatetruecolor(intval(1000 * ($this_imagesize[0] / $this_imagesize[1])), 1000);

        imagecopyresampled($thumbnail, $thumb_source, 0, 0, 0, 0, intval(1000 * ($this_imagesize[0] / $this_imagesize[1])), 1000, $this_imagesize[0], $this_imagesize[1]);

        unlink('/path/' . $this_image_id . '.jpg');

        imagejpeg($thumbnail, '/path/' . $this_image_id . '.jpg', 75);
    }