Issue: 

How to set the background transparency for TIF format raster images?

Solution:

Method 1:
After inserting the TIF image, select the raster image.
In the Properties panel (shortcut Ctrl+1), change the Background Transparency setting to Yes to complete the setup.

Method 2:
Enter the command TRANSPARENCY and set its value to ON.


CN Solution★中望CAD中TIF光栅图像如何设置背景透明度
JP Solution

★How to set background transparency for TIF raster images in ZWCAD：https://confluence.zwcad.com/pages/viewpage.action?pageId=316574476