12. A computer-readable storage medium having computer-executable instructions recorded thereon, the computer-executable instructions to configure a computer to perform operations comprising: obtaining an image; defining a region of visual context in the image; identifying one or more local interest points in the region of visual context; partitioning the region of visual context into sectors; producing a sub-histogram for each sector, wherein the sub-histograms represent which of the sectors contain which of the one or more local interest points; concatenating the sub-histograms produced for each sector to generate a histogram describing a contextual distribution of the region of visual context; and storing the histogram describing the contextual distribution of the region of visual context.
12. A computer-readable storage medium having computer-executable instructions recorded thereon, the computer-executable instructions to configure a computer to perform operations comprising: obtaining an image; defining a region of visual context in the image; identifying one or more local interest points in the region of visual context; partitioning the region of visual context into sectors; producing a sub-histogram for each sector, wherein the sub-histograms represent which of the sectors contain which of the one or more local interest points; concatenating the sub-histograms produced for each sector to generate a histogram describing a contextual distribution of the region of visual context; and storing the histogram describing the contextual distribution of the region of visual context. 14. A computer-readable storage medium as recited in claim 12 , the operations further comprising calculating a circle distance between the sectors in the region of visual context.