sfs_pentland ( Image : Height : Slant, Tilt, Albedo, Ambient : )
Reconstruct a surface from a gray value image.
sfs_pentland reconstructs a surface (i.e., the relative
height of each image point) using the algorithm of Pentland. The
surface is reconstructed from the input image Image, and
the light source given by the parameters Slant,
Tilt, Albedo and Ambient, and is
assumed to lie infinitely far away in the direction given by
Slant and Tilt. The parameter
Albedo determines the albedo of the surface, i.e., the
percentage of light reflected in all directions. Ambient
determines the amount of ambient light falling onto the surface. It
can be set to values greater than zero if, for example, the white
balance of the camera was badly adjusted at the time the image was
taken.
Attention
sfs_pentland assumes that the heights are to be
extracted on a lattice with step width 1. If this is not the case,
the calculated heights must be multiplied by the step width after
the call to sfs_pentland. A Cartesian coordinate system
with the origin in the lower left corner of the image is used
internally. Because the operator is based on the Fast Fourier
Transform, only square images with the edge length being a power of
2 are accepted. sfs_pentland can only handle
byte-images.
Parameters
Image (input_object)
|
image(-array) -> object
|
Shaded input image. |
Height (output_object)
|
image(-array) -> object
|
Reconstructed height field. |
Slant (input_control)
|
angle.deg -> real / integer
|
Angle of the light source and the positive z-axis
(in degrees). |
Default value: 45.0 |
Suggested values: 1.0, 5.0, 10.0, 20.0, 40.0, 60.0, 90.0 |
Range of values: 0.0 <= Slant <= 180.0 (lin) |
Minimum increment: 1.0
|
Recommended increment: 10.0
|
Tilt (input_control)
|
angle.deg -> real / integer
|
Angle between the light source and the x-axis after
projection into the xy-plane (in degrees). |
Default value: 45.0 |
Suggested values: 1.0, 5.0, 10.0, 20.0, 40.0, 60.0, 90.0 |
Range of values: 0.0 <= Tilt <= 360.0 (lin) |
Minimum increment: 1.0
|
Recommended increment: 10.0
|
Albedo (input_control)
|
number -> real / integer
|
Amount of light reflected by the surface. |
Default value: 1.0 |
Suggested values: 0.1, 0.5, 1.0, 5.0 |
Range of values: 0.0 <= Albedo <= 5.0 (lin) |
Minimum increment: 0.01
|
Recommended increment: 0.1
|
Restriction: Albedo >= 0.0 |
Ambient (input_control)
|
number -> real / integer
|
Amount of ambient light. |
Default value: 0.0 |
Suggested values: 0.1, 0.5, 1.0 |
Range of values: 0.0 <= Ambient <= 1.0 (lin) |
Minimum increment: 0.01
|
Recommended increment: 0.1
|
Restriction: Ambient >= 0.0 |
Result
If all parameters are correct sfs_pentland returns the
value TRUE. Otherwise, an exception is raised.
Possible Predecessors
estimate_al_am,
estimate_sl_al_lr,
estimate_sl_al_zc,
estimate_tilt_lr,
estimate_tilt_zc
Possible Successors
shade_height_field
Copyright © 1996-1997 MVTec Software GmbH