I have Landsat 5-8 images, and after creating subset for the area of interest there is an empty border on the image as black part. How to remove it or how to create subset without it? Here is the view of the subset image after multiresolution segmentation that shows there were segmented the empty part of image, too (black part beside the image):
There is the option to assign a certain value (which you can define e.eg. while exporting data from ArcGIS) as NoData once you start a new project and select the image you want to work on. See User Guide ecognition 9.0 - "6.2.4 Assigning No-Data Values"