Assignment 1

Bitmap Effect

3D city models are often equipped with cartoonish, flat-color textures. These can be stored at lower resolution, they fit to the blocky look of the buildings' shapes, and they are easier to comprehend for the user. To create these textures, photographs of the the facades are taken and then processed accordingly. The first step is to rectify the images (i.e., to undo the perspective distortion); the second step is to eliminate details and to correct the colors to brighten up shadows. Develop and implement a program for this second step. It should load a bitmap file, process it, and write the result back to disk.

original facade image
Input: Photograph after rectification

image after processing
Output: Result after processing (done manually for this example)

Focus on either the elimination of image detail (but don't blur the edges) or on shadow removal. You may use any appropriate algorithm you find or invent, such as median filter or bilateral filter for detail elimination or high-pass filtering of the brightness to remove soft shadows. Describe the algorithm and give its origin in the documentation. If you aim at four points for this assignment, try to come up with a complete solution for both detail elimination and shadow removal. To facilitate testing and/or adjustment, you may want to display intermediate results of your algorithm.

In the lab I'll hand out image examples from officials at Bremen and Düsseldorf. If you come up with a robust solution, they are going to give it a try.