Q: How can I remove the rectangular background of the raster data?

A: You can use the Raster Calculator con (Raster Data == Background Value, 0, 1) function to assign the value 0 to the background area, and assign 1 to the area that is not background. Then you can implement multiplication operation for the result dataset and the source raster dataset, and assign value 0 to the null value of the raster dataset to remove the background color.