Select the image layer and choose File > Export > Canvas Image/Mask Layer.
After you have created a sketch, you may want to export it as an image file.
You can export an image layer in 32 bit BMP format, so that the image file contains four channels (RGBA), or in 24 bit BMP format, so that the image file contains three channels (RGB). Many graphics applications cannot read 32 bit BMP files. In these cases, export the image layer in 24 bit BMP format or use the imgcvt utility to convert the 32 bit BMP file to a 24 bit BMP file.
To export an entire canvas plane, you need to use File > Export > Make Canvas Picture.
To choose the image file format choose File > Export > Canvas Image/Mask Layer , choose the image file format (JPEG, ALS, TIFF, 24 bit BMP, or 32 bit BMP), and click Go.