如何在OpenCV（Python）中将灰度图像转换为RGB，以便在处理二进制图像后可视化轮廓？ [英] How does one convert a grayscale image to RGB in OpenCV (Python) for visualizing contours after processing an image in binary?

问题描述

我正在学习使用OpenCV进行实时应用程序的图像处理。我对图像进行了一些阈值处理，并希望将轮廓标记为绿色，但它们没有显示为绿色，因为我的图像是黑白的。

I am learning image processing using OpenCV for a realtime application. I did some thresholding on an image and want to label the contours in green, but they aren't showing up in green because my image is in black and white.

早期在程序中我使用gray = cv2.cvtColor（frame，cv2.COLOR_BGR2GRAY）从RGB转换为灰度，但回去我很困惑，函数backtorgb = cv2.cvtColor（gray，cv2.CV_GRAY2RGB）给出了AttributeError ：'module'对象没有属性'CV_GRAY2RGB'。

Early in the program I used gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) to convert from RGB to grayscale, but to go back I am confused, and the function backtorgb = cv2.cvtColor(gray,cv2.CV_GRAY2RGB) is giving AttributeError: 'module' object has no attribute 'CV_GRAY2RGB'.

下面的代码似乎没有以绿色绘制轮廓 - 这是因为它是灰度图像吗？如果是这样，我可以将灰度图像转换回RGB以使绿色轮廓可视化吗？

The code below does not appear to be drawing contours in green - is this because it's a greyscale image? If so, can I convert the grayscale image back to RGB to visualize the contours in green?

import numpy as np
import cv2
import time

cap = cv2.VideoCapture(0)
while(cap.isOpened()):

    ret, frame = cap.read()

    gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)

    ret, gb = cv2.threshold(gray,128,255,cv2.THRESH_BINARY)

    gb = cv2.bitwise_not(gb)

    contour,hier = cv2.findContours(gb,cv2.RETR_CCOMP,cv2.CHAIN_APPROX_SIMPLE)

    for cnt in contour:
        cv2.drawContours(gb,[cnt],0,255,-1)
    gray = cv2.bitwise_not(gb)

    cv2.drawContours(gray,contour,-1,(0,255,0),3)

    cv2.imshow('test', gray)

    if cv2.waitKey(1) & 0xFF == ord('q'):
        break

cap.release()
cv2.destroyAllWindows()

推荐答案

我正在推广我的评论答案：

I am promoting my comment to an answer:

简单的方法是：

您可以使用原始的框架本身而不是使用灰色图像。

You could draw in the original 'frame' itself instead of using gray image.

困难的方法（你试图实施的方法）：

The hard way (method you were trying to implement):

backtorgb = cv2.cvtColor（gray，cv2.COLOR_GRAY2RGB）是正确的语法。

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