在无网格图像Python Opencv上画线

Question

我在下面有一张这样的图片。 [![在此处输入图像描述][2]][2] 我尝试在行和列之间添加垂直线和水平线。我使用[这里][1]提供的代码成功地添加了水平的。但我没有添加垂直的。谁能帮忙指出我的代码出了什么问题？

import cv2
import numpy as np
import matplotlib.pyplot as plt
file = r"C:/Users/gaojia/Dropbox/Projects/Parking_lot/Community_Group_Buying/scripts/test_2.png"
# read image
img = cv2.imread(file)
hh, ww = img.shape[:2]

# convert to grayscale 
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

# threshold gray image
thresh = cv2.threshold(gray, 254, 255, cv2.THRESH_BINARY)[1]

# count number of non-zero pixels in each row
count = np.count_nonzero(thresh, axis=0)

# threshold count at ww (width of image)
count_thresh = count.copy()
count_thresh[count==hh] = 255
count_thresh[count<hh] = 0
count_thresh = count_thresh.astype(np.uint8)

# get contours
contours = cv2.findContours(count_thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
contours = contours[0] if len(contours) == 2 else contours[1]

# loop over contours and get bounding boxes and ycenter and draw horizontal line at ycenter
result = img.copy()
for cntr in contours:
    x,y,w,h = cv2.boundingRect(cntr)
    xcenter = x+w//2
    cv2.line(result, (xcenter,0), (xcenter, hh-1), (0, 0, 0), 2)


# display results
cv2.imshow("THRESHOLD", thresh)
cv2.imshow("RESULT", result)
cv2.waitKey(0)

上面的代码只在图像的最左边绘制了一条垂直线。我把原图中的竖线去掉了，结果还是一样。

------------编辑-------------------- ---------

与第一个答案一样，我意识到findContours() 的输入不应该是一维数组。因此，我替换了以下代码：

# count number of non-zero pixels in each row
count = np.count_nonzero(thresh, axis=0)

# threshold count at ww (width of image)
count_thresh = count.copy()
count_thresh[count==hh] = 255
count_thresh[count<hh] = 0
count_thresh = count_thresh.astype(np.uint8)

与：

# find row index with any value equals 0
row_zero = np.nonzero(np.any(thresh == 0, axis=1))[0]
# replace values in column with any 0 with 0.
thresh[row_zero, :] =  0

这会在文本列之间添加垂直线。 [1]：Python & OpenCV: How to add lines to gridless table [2]：https://i.stack.imgur.com/YnPns.png

Answer 1

您的问题是，无论沿轴 0 还是轴 1，计数都是一维的。因此，您必须像在 Python/OpenCV 中一样使用边界框中的 x,y 和 w,h。

输入：

import cv2
import numpy as np

# read image
img = cv2.imread("gridless_table.png")
hh, ww = img.shape[:2]

# convert to grayscale 
gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)

# threshold gray image
thresh = cv2.threshold(gray, 254, 255, cv2.THRESH_BINARY)[1]

# count number of non-zero pixels in each column
count = np.count_nonzero(thresh, axis=0)

# threshold count at hh (height of image)
count_thresh = count.copy()
count_thresh[count==hh] = 255
count_thresh[count<hh] = 0
count_thresh = count_thresh.astype(np.uint8)

# get contours
contours = cv2.findContours(count_thresh, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_SIMPLE)
contours = contours[0] if len(contours) == 2 else contours[1]

# loop over contours and get bounding boxes and xcenter and draw vertical line at ycenter
result = img.copy()
for cntr in contours:
    # must transpose x,y and w,h since count is one-dimensional but represents each column
    y,x,h,w = cv2.boundingRect(cntr)
    print(x,y,w,h)
    xcenter = x+w//2
    cv2.line(result, (xcenter,0), (xcenter, hh-1), (0, 0, 0), 2)

# save results
cv2.imwrite("gridless_table_lines.png", result)

# display results
cv2.imshow("THRESHOLD", thresh)
cv2.imshow("RESULT", result)
cv2.waitKey(0)

结果：