I can't find any information on how pixels are selected as being a part of an ROI if the ROI was created using a vector layer which contains partial pixels. I'm trying to export my roi to ascii and am cross checking to see which pixels are actually exported. I thought it might be if the ROI just touches a pixel it would be included, but that doesn't seem to be the case. Then i thought it was the centroid of the pixel, but that isn't it either. what is the selection criteria? and is there an ability to change it? for example if i wanted to include all pixels that the ROI touches, no matter how much of the pixel it covers. I'm working on ENVI 4.0 on windows thanks Dillon