Graphics. Fromimage reports an error "graphics object cannot be created from an image that has an indexed pixel..."

   test OCR modular PaddleSharp In the process , In order to draw a rectangle containing text blocks in the picture , use Graphics.FromImage Function to get the drawing object of the picture . When testing with the pictures in the previous article ,jpg Pictures can be drawn normally , But test references 1 in png Format of ID card picture , The program reported the following error ：
  A Graphics object cannot be created from an image that has an indexed pixel format. (Parameter ‘image’)
   from MSDN see , call Graphics.FromImage Exception in function , An exception will be thrown when the picture has index pixel format or the format is not defined , The errors encountered in this article refer to indexed pixel Index pixel , Therefore, it should be that the tested image format does not support Graphics.FromImage.

   reference 3 This paper introduces the index pixel format picture , Its common format is gif and png, The main purpose is to reduce the picture size . reference 4 Index pixel format image creation is given in Graphics Common handling of objects , Copy the picture to another Bitmap Object before using Graphics.
   For the question of this article , There are two ways , One is to program png Convert the picture to bmp or jpg Format and then draw a rectangle containing a text block , The other is to manually save the picture as jpg or bmp Format .
   Because there is only one wrong picture in the test picture , Simplicity , Directly use the drawing board to save it as jpg, rerun routine , It can be created normally Graphics Object and draw a rectangle containing a text block , The effect drawing is shown in the figure below （ The test pattern is derived from references 1）.

reference ：
[1]http://news.sohu.com/a/524033869_121124363
[2]https://docs.microsoft.com/zh-cn/dotnet/api/system.drawing.graphics.fromimage?redirectedfrom=MSDN&view=dotnet-plat-ext-6.0#System_Drawing_Graphics_FromImage_System_Drawing_Image_
[3]https://wenku.baidu.com/view/9db4726b757f5acfa1c7aa00b52acfc789eb9f99.html
[4]https://blog.csdn.net/w6579106/article/details/115865396