vstereo(1)

PROGRAM
vstereo - Computes the depth in a matched pair of stereo image

SYNTAX

vstereo

-i  Input Matched Image

-o  Output Depth Image

[-f]
    Focal Length of the Camera

[-l]
    Image Length (CCD Sensor)

[-h]
    Image Height (CCD Sensor)

[-d]
    Camera Displacement on X Axis

[-z]
    Maximum Distance from camera

[-V]
    Gives the version for vstereo

[-U]
    Gives the usage for vstereo

[-P]
    Prompts for command line options

[-A [file1]]
    Creates the answer file called vstereo.ans or file1

[-a [file1]]
    Uses vstereo.ans or file1 as the answer file

DESCRIPTION

vstereo analyzes an image produced by the routine vrmatch and produces an image in which the pixel value correspond to its distance from the camera. Then the input image produced by vrmatch has to contain in its left part the image issued from the left camera and the one issued from the right camera in its right part.

Vstereo needs to know the following parameters:

    The Focal Length of the Camera.

    The Length of the image inside the camera (CCD matrix)

    The Height of the image inside the camera (CCD matrix).

    The distance of the two camera (left and right).

    The distance that can be considered as the background.

The Algorithm works this way:

First of all, the input image contains region based segmentated images with the image from the left camera on the left side and the right one on the right side.

In both the left and right images, the regions that have been matched have the same label (label number starting at 1).

Then the process will be to find the centroid of these regions then computes the depth from the left and right centroid (cf Stereo formulas at the end of this description).

The principle remains simple and gives acceptable results if the labelling process gives a precise location of the border of the region in both left and right images.

A problem can happened if the region is not entirely in the image because in this case the position of the centroid will not be defined with accuracy.

Another problem that happened is that sometimes, the result obtained are not accurate enough to keep them. In this case the distance of the object from the camera will be set to 0. This way we can give the original image and the result one to another stereo algorithm based on a different approach (contour matching or point to point correspondance) and improved the information in the entire distance image.

The last comment will be about the background distance that the user has to give in the command line or the graphic interface. This value defines the distance over which the result doesn't matter anymore. Whatever region would be further than this maximum distance would be automatically set to the background. In robotics for example, you want to be abble to say to the robot that something is at a distance less then 2 meters from the camera, but you don't care about things that are further than that distance.

STEREO formulas.

    x (left image)/focal length = X (real world) / Z (real world)

    x (right image) / focal =(X - camera displacement)/ Z (real world)

    Z (real world) = /x_left - x_right / camera_displacement * focal_length

REQUIRED ARGUMENTS

-i  type: infile
    desc: Input Matched Image

-o  type: outfile
    desc: Output Depth Image

OPTIONAL ARGUMENTS

-f  type: float
    desc: Focal Length of the Camera
    default: 30
    bounds: 0.000000 < [-f] < 100.000000

-l  type: float
    desc: Image Length (CCD Sensor)
    default: 10
    bounds: 0.000000 < [-l] < 30.000000

-h  type: float
    desc: Image Height (CCD Sensor)
    default: 10
    bounds: 0.000000 < [-h] < 30.000000

-d  type: float
    desc: Camera Displacement on X Axis
    default: 100
    bounds: 0.000000 < [-d] < 100000.000000

-z  type: float
    desc: Maximum Distance from camera
    default: 6000
    bounds: 0.000000 < [-z] < 10000.000000

EXAMPLES
vstereo -i reg_match.xv -o depth.xv -f 50.0 -l 10.0 -h 7.0 -d 30.0 -z 7000.0

All the value have to be given in millimeters.

This command will computes the distance from the camera for each point belonging to a region in the input image.

SEE ALSO
intro(1), verror(3), vgparms(3), vutils(3), lvstereo(3)

RESTRICTIONS

COPYRIGHT
Copyright 1991, University of New Mexico. All rights reserved.