如何在OpenCV(Python)中将灰度图像转换为RGB? [英] How does one convert a grayscale image to RGB in OpenCV (Python)?

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，但是由于我的图像是黑白图像，所以它们没有显示为绿色.

I'm 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.

在程序的早期，我曾使用gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY)从RGB转换为灰度，但是回过头来，我感到很困惑，并且函数backtorgb = cv2.cvtColor(gray,cv2.CV_GRAY2RGB)给出了:

Early in the program I used gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) to convert from RGB to grayscale, but to go back I'm confused, and the function backtorgb = cv2.cvtColor(gray,cv2.CV_GRAY2RGB) is giving:

AttributeError:模块"对象没有属性"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，以绿色显示轮廓吗?

The code below does not appear to be drawing contours in green. Is this because it's a grayscale 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

我正在对评论发表评论:

I am promoting my comment to an answer:

简单的方法是:

您可以自己绘制原始的框架"，而不用使用灰色图像.

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

困难的方法(您尝试实现的方法):

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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