Median filtering with different rank masks.
The operator ::median_image carries out a non-linear smoothing of the gray values of all input images (Image). The shift mask (MaskType) is transmitted in the form of an object (more precisely: its region). Several margin controls can be chosen for filtering (Margin):
0...255 pixels outside of the image edges
are assumed constant (with the indicated
gray value).
-1 Continuation of edge pixels.
-2 Cyclic continuation of image edges.
-3 Reflection of pixels at the image edges.
The indicated mask (= region of the mask image) is put over the
image to be filtered in such a way that the center of the mask
touches all pixels of the objects once. For each of these pixels
all neighboring pixels covered by the mask are sorted in an
ascending sequence according to their gray values. Thus, each of
these sorted gray value sequences contains exactly as many gray
values as the mask has pixels. From these sequences the median is
selected and entered as resulting gray value at the corresponding
output image.
|
Image (input_object) |
(multichannel-)image(-array) -> Hobject: HImage(Array) ( byte ) |
| Image to be filtered. | |
|
ImageMedian (output_object) |
(multichannel-)image(-array) -> Hobject * : HImage(Array) ( byte ) |
| Median filtered image. | |
|
MaskType (input_control) |
string -> HTuple.char * |
| Type of median mask. | |
| Default value: 'circle' | |
| List of values: 'circle', 'rectangle' | |
|
Radius (input_control) |
integer -> HTuple.long |
| Radius of median mask. | |
| Default value: 1 | |
| Suggested values: 1, 2, 3, 4, 5, 6, 7, 8, 9, 11, 15, 19, 25, 31, 39, 47, 59 | |
| Typical range of values: 1 <= Radius <= 101 | |
| Minimum increment: 1 | |
|
Recommended increment: 2 | |
|
Margin (input_control) |
integer -> HTuple.long |
| Margin control: 0...255 (constant), -1 (edge pixels continued), -2 (cyclic continuation), -3 (reflection). | |
| Default value: -3 | |
| Typical range of values: -3 <= Margin <= 255 | |
read_image(&Image,"fabrik"); median_image(Image,&Median,"circle",3,-1); disp_image(MedianWeighted,WindowHandle);
For each pixel: O(sqrt(F) * 5) with F = area of MaskType.
If the parameter values are correct the operator ::median_image returns the value 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 handling is raised.
::threshold, ::dyn_threshold, ::regiongrowing
::gen_circle, ::gen_rectangle1, ::gray_erosion_rect, ::gray_dilation_rect
R. Haralick, L. Shapiro; ``Computer and Robot Vision''; Addison-Wesley, 1992, Seite 318-319
Image filters
