Mathematical methods of Thinking-python computing Warfare (8)-Machine vision-Two value

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Hreshold

Applies a fixed-level threshold to each array element.

C + +:   double  threshold ( inputarray  src , outputarray  DST , DOUBLE&N Bsp Thresh , double maxval , int  type )

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

Highlight=cvthreshold #cv2. Threshold "title=" permalink to this definition "style=" Color:rgb (101, 161, 54); Text-decoration:none; Visibility:hidden; Font-size:0.8em; padding:0px 4px; "

C: Double cvthreshold (const cvarr* src, cvarr* DST, double Threshol D, double max_value, int threshold_type )

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 andthresh_binary_inv thresholding types. type –thresholding type (see the details below).

the function applies fixed-level thresholding to a single-channel array. The function is typically used to get a bi-level (binary) image out of a grayscale image (compare ()  could be also used for the purpose) or for removing a noise, which is, Filte Ring out pixels with too small or too large values. There is several types of thresholding supported by the function. They is determined by type  :

• Thresh_binary

• Thresh_binary_inv

• Thresh_trunc

• Thresh_tozero

• Thresh_tozero_inv

Also, the special value Thresh_otsu is combined with one of the above values. In this case, the function determines the optimal threshold value using the Otsu ' s algorithm and uses it instead of the SP Ecified thresh . The function returns the computed threshold value. Currently, the Otsu ' s method is implemented only for 8-bit images.

Import cv2fn= "test3.jpg" Myimg=cv2.imread (FN) Img=cv2.cvtcolor (myimg,cv2. Color_bgr2gray) retval, Newimg=cv2.threshold (img,40,255,cv2. thresh_binary) cv2.imshow (' Preview ', newimg) Cv2.waitkey () cv2.destroyallwindows ()

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Adaptive binary

The adaptivethreshold function can be two-valued and can also extract edges:

Python: cv2. Adaptivethreshold (src, maxValue, Adaptivemethod, Thresholdtype, BlockSize, C[, DST]) →DST

C:  void Cvadaptivethreshold (Const cvarr* src, cvarr* DST, double Max_valueInt Adaptive_method=cv_adaptive_thresh_mean_c, int Threshold_type=cv_thresh_binary, int block_size=3, double param1=5 )

Highlight=cvthreshold#void cvadaptivethreshold (const cvarr* SRC, cvarr* DST, double max_value, int adaptive_method, int t Hreshold_type, int block_size, double param1) "title=" permalink to this definition "style=" Color:rgb (101, 161, 54); Text-decoration:none; Visibility:hidden; Font-size:0.8em; padding:0px 4px; " >

src –source 8-bit single-channel image. DST –destination image of the same size and the same type as src . maxValue –non-zero value assigned to the pixels for which, the condition is satisfied. See the details below. adaptivemethod –adaptive thresholding algorithm to use,adaptive_thresh_mean_c oradaptive_ Thresh_gaussian_c . See the details below. thresholdtype –thresholding type that must is eitherthresh_binary or thresh_binary_inv . blockSize –size of a pixel neighborhood that's used to calculate a threshold value for the Pixel:3, 5, 7, and So on. C –constant subtracted from the mean or weighted mean (see the details below). Normally, it is positive and may are zero or negative as well. The Block_size parameter determines the size of the block of the local threshold. Block very hour. such as block_size=3 or 5 or 7 o'clock, the performance of the edge extraction function. When the block_size is set to a larger value, such as block_size=21, 51, etc., it is two value The following is the extraction edge Import cv2fn= "test3.jpg" Myimg=cv2.imread (FN) Img=cv2.cvtcolor (myimg,cv2. Color_bgr2gray) Newimg=cv2.adaptivethreshold (img,255,cv2. Adaptive_thresh_mean_c,cv2. thresh_binary,5,2) cv2.imshow (' Preview ', newimg) Cv2.waitkey () cv2.destroyallwindows () watermark/2/text/ahr0cdovl2jsb2cuy3nkbi5uzxqvbxloyxnwba==/font/5a6l5l2t/fontsize/400/fill/i0jbqkfcma==/ Dissolve/70/gravity/southeast "/> binary such as the following: Import cv2fn= "test3.jpg" Myimg=cv2.imread (FN) Img=cv2.cvtcolor (myimg,cv2. Color_bgr2gray) Newimg=cv2.adaptivethreshold (img,255,cv2. Adaptive_thresh_mean_c,cv2. thresh_binary,51,2) cv2.imshow (' Preview ', newimg) Cv2.waitkey () cv2.destroyallwindows ()

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Mathematical methods of Thinking-python computing Warfare (8)-Machine vision-Two value