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



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