Query by synthesized sketch in an architectural database
Résumé
In an architectural database that is to be used by architects, urbanists, sociologists, geometers, etc., querying must be simplified. The aim of this work is to retrieve the images of a building that best fit a specified point of view. Original data are provided in DXF and TIFF formats (maps and images respectively.) A loose linking between these two types of information is obtained through textural attributes. However, the same building is photographed several times and more than a single building can appear on a picture. After determining the point of view by simple `clicks' on a map, we take advantages of the geometrical description of the building in order to draw its outline. Then, the images that have been textually associated with the selected building undergo a five-steps image-processing algorithm: conversion from the RGB color- space to intensity component, Nagao filtering, oriented gradient filtering, thresholding, and correlation-based hierarchical full search matching. If the building objects are not completely masked by natural ones, the `rectangular' shapes of frontage and side walls correspond well to the sketch and the requested images are returned to the user.