###### tags: `OpenCV`,`影像處理`,`素描照`
# OpenCV 實作篇-利用CV2來畫個半邊素描照吧

#讀進照片
import cv2
img= cv2.imread('pregnant.jpg') #使用我懷孕時的照片
cv2.imshow("pregnant",img)  
cv2.waitKey(0)
cv2.destroyAllWindows()
#照片尺寸
img.shape #(627, 418, 3)


#取右半部
cv2.imshow("pregnant_half",img[:,209:,:])  
cv2.waitKey(0)
cv2.destroyAllWindows()


#開始處理
img_half=img[:,209:,:]
gray_image = cv2.cvtColor(img_half, cv2.COLOR_RGB2GRAY) #右邊一半圖形先轉變灰階
inv_gray = 255 - gray_image #再將色調改變 (黑變白,白變黑)
blurred_image = cv2.GaussianBlur(inv_gray, (13, 13), 0, 0) #利用高斯模糊調整一下(搭配模糊降噪效果較佳)
gray_sketch = cv2.divide(gray_image, 255 - blurred_image, scale=256) #針對右半部的gary_image去做divide
gray_sketch =cv2.cvtColor(gray_sketch, cv2.COLOR_GRAY2BGR)#再將grayimage還原回BGR
img[:,209:,:]=gray_sketch #將照片再結合回去
cv2.imshow("pregnant_finish",img)
cv2.waitKey(0)
cv2.destroyAllWindows()


conference:
<https://docs.opencv.org/3.4/d2/de8/group__core__array.html#ga6db555d30115642fedae0cda05604874>
**divide(src1, src2, dst=None, scale=None, dtype=None)**
**src1:** first input array.
**src2:** second input array of the same size and type as src1.
**scale:** scalar factor.
**dst:** output array of the same size and type as src2.
dtype,optional depth of the output array; if -1, dst will have depth src2.depth(), but in case of an array-by-array division, you can only pass -1 when src1.depth()==src2.depth().

The function cv::divide divides one array by another:
dst(I) = saturate(src1(I)*scale/src2(I))

or a scalar by an array when there is no src1 :
dst(I) = saturate(scale/src2(I))

When src2(I) is zero, dst(I) will also be zero. Different channels of multi-channel arrays are processed independently.

:star:補充說明

inv_gray = 255 - gray_image
cv2.imshow("gray_image",gray_image) 
cv2.imshow("inv_gray",inv_gray) 
cv2.waitKey(0)
cv2.destroyAllWindows()

#暗的部分變亮  亮的部分變暗
#這就是要把我們圖裡面的邊框給選出來