ComPDFKit（win）- 补充数字签名多种图片格式

Demo/Examples/Compdfkit_Tools/DigitalSignature/FillDigitalSignatureControl/FillDigitalSignatureControl.xaml.cs

@@ -402,7 +402,8 @@ namespace Compdfkit_Tools.PDFControl
 
         private void BrowseTxt_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
         {
-            string pngPath = CommonHelper.GetExistedPathOrEmpty("PNG files (*.png)|*.png");
+            string filter = "Image files (*.jpg, *.jpeg, *.png, *.bmp)|*.jpg;*.jpeg;*.png;*.bmp";
+            string pngPath = CommonHelper.GetExistedPathOrEmpty(filter);
             if (!string.IsNullOrEmpty(pngPath))
             {
                 imagePath = pngPath;