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fast_threshold — Fast thresholding of images using global thresholds.
fast_threshold selects the pixels from the input image whose gray values g fulfill the following condition:
To reduce the processing time, the selection is done in two steps: At first, all points lying on selected horizontal lines that are specified by their distance MinSize are processed. In the next step the neighborhood (size (2*MinSize+1) x (2*MinSize+1)) of all previously selected points are processed.
On multicore computers supporting the SSE2 instruction set, threshold is most likely faster than fast_threshold. fast_threshold may only be preferred to threshold if those features are not available, e.g. on embedded platforms.
Input image.
Segmented regions.
Lower threshold for the gray values.
Default value: 128
Suggested values: 0.0, 10.0, 30.0, 64.0, 128.0, 200.0, 220.0, 255.0
Typical range of values: 0.0 ≤ MinGray ≤ 255.0 (lin)
Minimum increment: 1
Recommended increment: 5.0
Upper threshold for the gray values.
Default value: 255.0
Suggested values: 0.0, 10.0, 30.0, 64.0, 128.0, 200.0, 220.0, 255.0
Typical range of values: 0.0 ≤ MaxGray ≤ 255.0 (lin)
Minimum increment: 1
Recommended increment: 5.0
Minimum size of objects to be extracted.
Default value: 20
Suggested values: 5, 10, 15, 20, 25, 30, 40, 50, 60, 70, 100
Typical range of values: 2 ≤ MinSize ≤ 200 (lin)
Minimum increment: 1
Recommended increment: 2
Let A be the area of the output region and height the height of Image. Then the runtime complexity is O(A + height / MinSize).
fast_threshold returns 2 (H_MSG_TRUE) if all parameters are correct. The behavior with respect to the input images and output regions can be determined by setting the values of the flags 'no_object_result', 'empty_region_result', and 'store_empty_region' with set_system. If necessary, an exception is raised.
histo_to_thresh, min_max_gray, sobel_amp, binomial_filter, gauss_filter, reduce_domain, fill_interlace
connection, dilation1, erosion1, opening, closing, rank_region, shape_trans, skeleton
threshold, gen_grid_region, dilation_rectangle1, dyn_threshold
class_2dim_sup, hysteresis_threshold
Foundation
| Operators |