In 2006-2007, I created an application in C# to aid in the rapid labeling of images. The idea is to use polygonal regions to label areas of the image as one of two classes: groundplane or obstacle. Not all areas of the image will be labeled. For each image, a *.shp file is created which is a representation of the polygonal regions. Also, a *.msk file is created, which is a pixelwise or bitmap mask representation of the image, where each "pixel" in the mask has value of 0 (labeled as groundplane), 1 (labeled as obstacle), or 2 (not labeled). The polygonal regions can be preserved when labeling a subsequent image in the dataset, and can then be repositioned or modified accordingly to accurately label the regions as the appear in this new, presumably only slightly different, image.
Pixelwise Image Labeler runs on Windows 98/2000/XP/Vista and requires the Microsoft .NET Framework 1.1 or later (which is almost certainly already installed on your system).
Download Pixelwise Image Labeler.
Pixelwise Image Labeler v1.4, Copyright (C) 2006-2007, Michael J. Procopio.