python - 我如何更改此激光测距仪 python 代码以检测绿点而不是红点？

Question

所以我和我的 friend 们正在组装这个有人发布在这个网站上的自制激光测距仪:http://shaneormonde.wordpress.com/2014/01/25/webcam-laser-rangefinder/ .一切顺利，直到我们进入 python 代码部分，因为我们不熟悉任何编程语言。正如网站上的项目所描述的那样，它应该检测网络摄像头视野中的红点。不幸的是，我们已经购买了绿色激光器。您如何更改代码以使其检测到绿点？这是代码:

## program written by Shane Ormonde 7th sept 2013
## updated on 25th January 2014
## calculates the distance of a red dot in the field of view of the webcam.


import cv2
from numpy import *
import math

#variables
loop = 1

dot_dist = 0

cv2.namedWindow("preview")
vc = cv2.VideoCapture(1)



if vc.isOpened(): # try to get the first frame
    rval, frame = vc.read()

else:
    rval = False
    #print "failed to open webcam"


if rval == 1 :

    while loop == 1:
            cv2.imshow("preview", frame)
            rval, frame = vc.read()
            key = cv2.waitKey(20)
            if key == 27: # exit on ESC
                loop = 0
            num = (frame[...,...,2] > 236)
            xy_val =  num.nonzero()

            y_val = median(xy_val[0])
            x_val = median(xy_val[1])

            dist = ((x_val - 320)**2 + (y_val - 240)**2 )**0.5 # distance of dot from center pixel
            dist = abs(x_val - 320) # distance of dot from center x_axis only

            print " dist from center pixel is " + str(dist) 

            # work out distance using D = h/tan(theta)

            theta =0.0011450*dist + 0.0154         
            tan_theta = math.tan(theta)



            if tan_theta > 0: # bit of error checking
                obj_dist =  int(5.33 / tan_theta)


            print "\033[12;0H" + "the dot is " + str(obj_dist) + "cm  away"
elif rval == 0:
        print " webcam error "    

Answer 1

rval, frame = vc.read() 读取 BGR 格式的图像。您直接链接的教程页面说明了这一点。

So all of the pixel data is stored in a numpy array called frame. By default opencv grabs a 640 x 480 image ( thats 640 on the x-axis and 480 on the y ). The numpy array has three dimensions, (x)(y)(BGR), so the first two dimensions have just one number in each specifying the x or y co-ordinate of the pixel. The third dimension contains three numbers, the RGB content of that pixel. Although for some reason the values are arranged BGR.

因此，换行

num = (frame[...,...,2] > 236)

到

num = (frame[...,...,1] > 236)

应该能帮到你。

为了非常简要地解释这条线的作用，它检查颜色平面中的高强度值(超过 236 - 其中 min=0 和 max=255)并记录所有这些像素。这个想法是，如果你发射红色激光，红色平面将在点区域周围集中高强度值。