threshold

最新推荐文章于 2024-09-04 10:47:11 发布

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Applies a fixed-level threshold to each array element.

C++: double threshold (InputArray src, OutputArray dst, double thresh, double maxval, int type )

Python: cv2. threshold (src, thresh, maxval, type [, dst ] ) → retval, dst

C: double cvThreshold (const CvArr* src, CvArr* dst, double threshold, double max_value, int threshold_type )

Python: cv. Threshold (src, dst, threshold, maxValue, thresholdType ) → None

Parameters:	src – input array (single-channel, 8-bit or 32-bit floating point). dst – output array of the same size and type as `src`. thresh – threshold value. maxval – maximum value to use with the `THRESH_BINARY` and `THRESH_BINARY_INV` thresholding types. type – thresholding type (see the details below).

The function applies fixed-level thresholdingto a single-channel array. The function is typically used to get abi-level (binary) image out of a grayscale image (compare() couldbe also used for this purpose) or for removing a noise, that is, filteringout pixels with too small or too large values. There are severaltypes of thresholding supported by the function. They are determined by type :

THRESH_BINARY

$\texttt{dst} (x,y) = \fork{\texttt{maxval}}{if $\texttt{src}(x,y) > \texttt{thresh}$}{0}{otherwise}$

THRESH_BINARY_INV

$\texttt{dst} (x,y) = \fork{0}{if $\texttt{src}(x,y) > \texttt{thresh}$}{\texttt{maxval}}{otherwise}$

THRESH_TRUNC

$\texttt{dst} (x,y) = \fork{\texttt{threshold}}{if $\texttt{src}(x,y) > \texttt{thresh}$}{\texttt{src}(x,y)}{otherwise}$

THRESH_TOZERO

$\texttt{dst} (x,y) = \fork{\texttt{src}(x,y)}{if $\texttt{src}(x,y) > \texttt{thresh}$}{0}{otherwise}$

THRESH_TOZERO_INV

$\texttt{dst} (x,y) = \fork{0}{if $\texttt{src}(x,y) > \texttt{thresh}$}{\texttt{src}(x,y)}{otherwise}$

Also, the special value THRESH_OTSU may be combined withone of the above values. In this case, the function determines the optimal thresholdvalue using the Otsu’s algorithm and uses it instead of the specified thresh .The function returns the computed threshold value.Currently, the Otsu’s method is implemented only for 8-bit images.