| Operators |
eliminate_min_max — Smooth an image in the spatial domain to suppress noise.
eliminate_min_max(Image : FilteredImage : MaskWidth, MaskHeight, Gap, Mode : )
eliminate_min_max smooths an image by replacing gray values with neighboring mean values, or local minima/maxima. In order to prevent edges and lines from being smoothed, only those gray values that represent local minima or maxima are replaced (if there is a line or edge within an image there will be at least one neighboring pixel with a comparable gray value). Gap controls the strictness of replacment: Only gray values that exceed all other values within their local neighborhood more than Gap and all values that fall below their neighboring more than Gap are replaced: E(x,y) represents a NxM sized rectangular neighborhood of an pixel at position (x,y), containing all pixels within the neighborhood except the pixel itself;
if gray_value(x,y) >= Gap + maximum(E(x,y)) then replacement;
else if gray_value(x,y) + Gap <= minimum(E(x,y)) then replacement;
else adopt gray_value(x,y) without change;
Mode specifies how to perform the new value in case of a replacement.
Mode = 1 --> replace a local maximum with next minor local maximum and replace a local minimum with next bigger local minimum
Mode = 2 --> replace with mean value of all pixels within the local neighborhood (including the replaced pixel)
Mode = 3 --> replace with median value of all pixels within the local neighborhood (including the replaced pixel (this is default and used if Mode has got any other value than 1 or 2)
MaskWidth and MaskHeight specifiy the width and height of the rectangular neighborhood. Border treatment: Pixels outside the image border are not considered (e.g.: With a local 3x3-mask the neighborhood of a pixel at (0,0) reduces to the pixels at (1,0),(0,1) and (1,1)).
For an explanation of the concept of smoothing filters see the introduction of chapter Filters / Smoothing.
eliminate_min_max only can work on byte images (HALCON image type BYTE_IMAGE). If MaskWidth or MaskHeight is an even number, it is replaced by the next higher odd number (this allows the unique extraction of the center of the filter mask). Width/height of the mask may not exceed the image width/height.
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 smooth.
Smoothed image.
Width of filter mask.
Default value: 3
Suggested values: 3, 5, 7, 9
Typical range of values: 3 ≤ MaskWidth ≤ width(Image)
Minimum increment: 2
Recommended increment: 2
Restriction: odd(MaskWidth)
Height of filter mask.
Default value: 3
Suggested values: 3, 5, 7, 9
Typical range of values: 3 ≤ MaskHeight ≤ width(Image)
Minimum increment: 2
Recommended increment: 2
Restriction: odd(MaskWidth)
Gap between local maximum/minimum and all other gray values of the neighborhood.
Default value: 1.0
Suggested values: 1.0, 2.0, 5.0, 10.0
Replacement rule (1 = next minimum/maximum, 2 = average, 3 =median).
Default value: 3
List of values: 1, 2, 3
eliminate_min_max returns 2 (H_MSG_TRUE) if all parameters are correct. If the input is empty eliminate_min_max returns with an error message.
mean_sp, mean_image, median_image, median_weighted, binomial_filter, gauss_filter, smooth_image
M. Imme:“A Noise Peak Elimination Filter”; S. 204-211 in CVGIP
Graphical Models and Image Processing, Vol. 53, No. 2, March 1991
M. Lückenhaus:“Grundlagen des Wiener-Filters und seine Anwendung in der
Bildanalyse”; Diplomarbeit;
Technische Universität München, Institut für Informatik;
Lehrstuhl Prof. Radig; 1995.
Foundation
| Operators |