In ArcGIS 10.6 I have a 3 Band tif image which has large areas which I do not want to display. I have created polygons of these areas and converted them to a raster tif in order to create a 4th band to use as an alpha channel to make areas transparent. I used the Composite band tool to create the 4 band raster but when I activate the alpha channel using this band the whole image becomes transparent and not just the defined areas.
The 4th Band consists of just 2 values 0 and 1. Is ArcGIS assuming that the extent of the 4th band is the transparent area and not just the pixels with a value of 1? How to I set the raster to only make pixel value 1 the transparent pixel.
I am aware than I can set a nodata color in ArcGIS but I need to try to do this using an alpha channel for a client.