Image From Bitmap
Created by using the gear menu
The Image variable has a channel structure that needs to be known even without data and will stay the same through all time values if there are more than one time value. This means for example that if the bitmap has an alpha channel and you are not picking an option that has an alpha channel it ignores that information. And if you ask for the alpha channel and the image doesn’t have any the value is 255.
Convertion from RGB to grayscale is using the expression
0.299*red + 0.587*green + 0.114*blue