The abcd method in the upper left corner of the picture is to use picture editing software and mobile phone picture editing software.

1. Use image editing software, such as Photoshop and GIMP. , add a text tool to the picture, and then enter the text "abcd".

2. Use mobile phone picture editing software, such as Meitu Xiu Xiu and PicsArt. , add a text tool to the picture, and then enter the text "abcd".