In Android Studio I imported pictures using File|New|image asset. Some pictures work fine but others are not only underlined with a zigzag red line in the project structure area but also I can't use them in my project. The images underlined with red are in the drawable folder. For example I imported a picture "pizza-small.jpg" and it didn't work. I tried to change the format using Gimp to a png picture but without success. I tried changing the resolution and aspect ration without success also.
I'm using Android Studio Arctic Fox. I googled the question many times without success.