dedecms水印无效

// 示例代码：添加文字水印
function addTextWatermark($sourceImage, $text, $position = 'bottomright', $opacity = 50) {
    $image = imagecreatefromjpeg($sourceImage);
    $textColor = imagecolorallocate($image, 255, 255, 255);
    $textX = 0;
    $textY = 0;

    switch ($position) {
        case 'topleft':
            $textX = 10;
            $textY = 10;
            break;
        case 'topright':
            $textX = imagesx($image) - 100;
            $textY = 10;
            break;
        case 'bottomleft':
            $textX = 10;
            $textY = imagesy($image) - 50;
            break;
        case 'bottomright':
        default:
            $textX = imagesx($image) - 100;
            $textY = imagesy($image) - 50;
            break;
    }

    imagestring($image, 5, $textX, $textY, $text, $textColor);
    imagejpeg($image, $sourceImage);
    imagedestroy($image);
}

// 使用示例
addTextWatermark('path/to/source/image.jpg', 'Watermark Text', 'bottomright', 50);