python - 在python(OpenCV)中查找对象的大小？

Question

如何使用python(opencv)获得明亮部分的高度和宽度？这些图片有2000个，最终目的是使表具有长度和宽度值

Answer 1

这是原始方法。转换为灰度并检查哪些点的值大于某些“明亮”的颜色，即。 21给出数组True/False-使用.any(axis=0)可以将每一行减少为单个值，使用.any(axis=1)可以将每一列减少为单个值，然后使用sum()您可以计算任何行或列中有多少True(因为True/False转换为1/0)

import cv2

img = cv2.imread('image.png')
img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
#print(img)

print('height, width, color:', img.shape)

#cv2.imshow('image', img)
#cv2.waitKey(0)
#cv2.destroyAllWindows()

print('width:', sum((img > 21).any(axis=0)))
print('height:', sum((img > 21).any(axis=1)))

为了你的形象，它给了我

width: 19
height: 27

对于我的形象(如下)，它给了我

width: 23
height: 128

编辑:版本，变化不大。

我将 mask = (img > 21)设置为

计算大小

创建黑白图像，更好地显示哪些点是
用于计算大小。

BTW:代码 ~mask反转掩码(将 True转换为 False和 False转换为 True)。它也可以用于反转图像- ~img-为RGB，灰度或黑白创建负片。

码:

import cv2

for filename in ['image-1.png', 'image-2.png']:

    img = cv2.imread(filename)
    img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

    print('height, width, color:', img.shape)

    mask = (img > 21)

    # display size 
    print(' width:', sum( mask.any(axis=0) ))
    print('height:', sum( mask.any(axis=1) ))

    # create Black&White version 
    img[  mask ] = 255 # set white
    img[ ~mask ] = 0   # set black

    # display Black&White version
    cv2.imshow('image', img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

    # write Black&White version
    cv2.imwrite('BW-' + filename, img)

--->

--->

编辑:使用 cv2.boundingRect()而不是 sum(mask.any())的结果相同-但仍需要 img[ mask ] = 255来创建黑白图像。

import cv2

for filename in ['image-1.png', 'image-2.png']:
    print('filename:', filename)

    img = cv2.imread(filename)
    #print('height, width, color:', img.shape)

    img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    #print('height, width, color:', img.shape)

    mask = (img > 21)

    # create Black&White version 
    img[  mask ] = 255 # set white
    img[ ~mask ] = 0   # set black

    x, y, width, height = cv2.boundingRect(img)

    # display size 
    print(' width:', width)
    print('height:', height)

    # display Black&White version
    #cv2.imshow('image', img)
    #cv2.waitKey(0)
    #cv2.destroyAllWindows()

    # write Black&White version
    #cv2.imwrite('BW-' + filename, img)

https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_contours/py_contour_features/py_contour_features.html#bounding-rectangle

编辑:使用 cv2.boundingRect()和 cv2.threshold()的结果相同-因此不需要 mask

import cv2

for filename in ['image-1.png', 'image-2.png']:
    print('filename:', filename)

    img = cv2.imread(filename)
    #print('height, width, color:', img.shape)

    img = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    #print('height, width, color:', img.shape)

    ret, img = cv2.threshold(img, 21, 255, cv2.THRESH_BINARY)  # the same 21 as in `mask = (img > 21)`
    x, y, width, height = cv2.boundingRect(img)

    # display size 
    print(' width:', width)
    print('height:', height)

    # display Black&White version
    cv2.imshow('image', img)
    cv2.waitKey(0)
    cv2.destroyAllWindows()

    # write Black&White version
    #cv2.imwrite('BW-' + filename, img)

https://docs.opencv.org/3.4/d7/d4d/tutorial_py_thresholding.html

https://opencv-python-tutroals.readthedocs.io/en/latest/py_tutorials/py_imgproc/py_thresholding/py_thresholding.html

https://www.learnopencv.com/opencv-threshold-python-cpp/

https://www.geeksforgeeks.org/python-thresholding-techniques-using-opencv-set-1-simple-thresholding/