ovl.detectors.threshold_detector module

class ovl.detectors.threshold_detector.ThresholdDetector(threshold: ovl.thresholds.threshold.Threshold, morphological_functions)

Bases: ovl.detectors.detector.Detector

ThresholdDetector is a detector used to find contours in a binary image. The binary image is created using a Threshold object. Examples of this are binary threshold, color, multicolor thresholds.

For more information on binary thresholding and color thresholding refer to the documentation of the relevant Threshold object and: Binary Thresholding - https://docs.opencv.org/3.4/d7/d4d/tutorial_py_thresholding.html Color Thresholding - https://docs.opencv.org/master/da/d97/tutorial_threshold_inRange.html

Threshold also allows the usage of morphological functions which are functions that are applied on the binary image created by the threshold.

Note

Morphological functions are functions decorated with @image_filter that act on binary images.

Examples for morphological functions are erosion or dilation.

For more information on morphological functions: https://docs.opencv.org/3.4/d9/d61/tutorial_py_morphological_ops.html

apply_morphological_functions(mask, morphological_functions=None)

Applies all morphological functions on the mask (binary images) created using the threshold, Morphological functions are functions that are applied to binary images to alter the shape of “detected” regions

Parameters:

• mask – the mask on which the functions should be applied
• morphological_functions – list of morphological_functions to be applied instead of self.morphological_functions

Returns:

the applied mask

apply_threshold(image: numpy.ndarray, threshold=None) → numpy.ndarray

Gets a mask (binary image) for a given image and Threshold object (uses self.threshold if given threshold was none)

Parameters:

• image – the numpy array of the image
• threshold – the Threshold object used to create the binary mask

Returns:

the binary mask

detect(image: numpy.ndarray, return_hierarchy=False, *args, **kwargs) → List[numpy.ndarray]

Gets a list of all the contours within the threshold that was given

Parameters:

• image – image from which to get the contours
• return_hierarchy – if the hierarchy should be returned

Returns:

list of all contours matching the range of hsv colours

find_contours_in_mask(mask: numpy.ndarray, return_hierarchy=False, apply_morphs=True) → List[numpy.ndarray]

This function is used to find and extract contours (object shapes) from a binary image (image passed through a threshold)

Parameters:

• mask – binary image (mask), a numpy array
• return_hierarchy – if the hierarchy should be returned
• apply_morphs – if the morphological functions should be applied.

Returns:

the list of contours