| Operators |
illuminate — Illuminate image.
illuminate(Image : ImageIlluminate : MaskWidth, MaskHeight, Factor : )
The operator illuminate enhances contrast. Very dark parts of the image are “illuminated” more strongly, very light ones are “darkened”. If orig is the original gray value and mean is the corresponding gray value of the low pass filtered image detected via the operators mean_image and filter size MaskHeight x MaskWidth. For byte-images val equals 127, for int2-images and uint2-images val equals the median value. The resulting gray value is new:
new = round ( (val - mean) * Factor + orig ).
The low pass should have rather large dimensions (30 x 30 to
200 x 200). Reasonable parameter combinations might be:
Height Width Factor
---------------------
40 40 0.55
100 100 0.7
150 150 0.8
i.e. the larger the low pass mask is chosen, the larger
Factor should be as well.
The following “spotlight effect” should be noted: If, for example, a dark object is in front of a light wall the object as well as the wall, which is already light in the immediate proximity of the object contours, are lightened by the operator illuminate. This corresponds roughly to the effect that is produced when the object is illuminated by a strong spotlight. The same applies to light objects in front of a darker background. In this case, however, the fictitious “spotlight” darkens objects.
Note that filter operators may return unexpected results if an image with a reduced domain is used as input. Please refer to the chapter Filters.
Image to be enhanced.
“Illuminated” image.
Width of low pass mask.
Default value: 101
Suggested values: 31, 41, 51, 71, 101, 121, 151, 201
Typical range of values: 3 ≤ MaskWidth ≤ 299
Minimum increment: 2
Recommended increment: 10
Height of low pass mask.
Default value: 101
Suggested values: 31, 41, 51, 71, 101, 121, 151, 201
Typical range of values: 3 ≤ MaskHeight ≤ 299
Minimum increment: 2
Recommended increment: 10
Scales the “correction gray value” added to the original gray values.
Default value: 0.7
Suggested values: 0.3, 0.5, 0.7, 1.0, 1.5, 2.0, 3.0, 5.0
Typical range of values: 0.0 ≤ Factor ≤ 5.0
Minimum increment: 0.01
Recommended increment: 0.2
Restriction: 0 < Factor && Factor < 5
read_image(Image,'fabrik') dev_display (Image) illuminate(Image,Better,40,40,0.55) dev_display (Better)
If the parameter values are correct the operator illuminate returns the value 2 (H_MSG_TRUE) The behavior in case of empty input (no input images available) is set via the operator set_system(::'no_object_result',<Result>:). If necessary an exception is raised.
scale_image_max, equ_histo_image, mean_image, sub_image
Foundation
| Operators |