How to write a python program to compare RGB values of thermal images to get the temperature?

Question

I am a high school student from Taiwan writing a program for a research project to compare RGB values of thermal images to the RGB values of the temperature bar to get the temperature of each pixel, then save it to an Excel file. The program was first written in MATLAB, and now I am rewriting it to Python. I already used SMOP to convert it and tried fixing it. However, there are still many problems I don't understand.

This is the Python code:

import cv2
import numpy
numpy.seterr(over='ignore')
import os
import pandas as pd

colorbar = cv2.imread(r'C:\Users\Pictures\Data\Colorbar.jpg')

num = 0
while num<=15300:
    picture = os.path.join(r'C:\Users\Pictures\Data\frame %d.jpg' %num)
    pic = cv2.imread(picture)
    h = 480
    w = 638
    k = 339
    min = 60
    temperature = numpy.linspace(25 + 273.15, 45 + 273.15, k)
    tem = temperature.T
    t = numpy.flipud(tem)
    pict = numpy.zeros((h, w))
    for i in numpy.arange(1, h).reshape(-1):
        for j in numpy.arange(1, w).reshape(-1):
            for n in numpy.arange(1, k).reshape(-1):
                dif_r = abs(pic[i, j, 0] - colorbar[n, 10, 0])
                dif_g = abs(pic[i, j, 1] - colorbar[n, 10, 1])
                dif_b = abs(pic[i, j, 2] - colorbar[n, 10, 2])
                d = dif_r + dif_g + dif_b
                if d < min:
                    pict[i, j] = t[n]
    num = num + 90

    df = pd.DataFrame(pict).T
    df.to_excel(excel_writer=r"C:\Users\Pictures\Data\frame %d.xlsx" %num)

This is the current error:

[ WARN:[email protected]] global D:\a\opencv-python\opencv-python\opencv\modules\imgcodecs\src\loadsave.cpp (239) cv::findDecoder imread_('C:\Users\Pictures\Data\frame 0.jpg'): can't open/read file: check file path/integrity
Traceback (most recent call last):
  File "C:\Users\PycharmProjects\MATLAB\main.py", line 24, in <module>
    dif_r = abs(pic[i, j, 0] - colorbar[n, 10, 0])
TypeError: 'NoneType' object is not subscriptable

This is the MATLAB code:

colorbar = imread(‘C:\Users\\Pictures\Data\Colorbar.jpg’);

for num = 90:+90:15300
    picture = fullfile(‘C:\Users\\Pictures\Data\’, sprintf(‘frame %d.jpg’, num));
    pic = imread(picture);

    h = 480;
    w = 638;
    k = 340;
    min  = 60;

    temperature = linspace(25+273.15, 45+273.15, k);
    tem = temperature’;
    t = flipud(tem);

    pict = zeros(h, w);
    for i = 1:h
        for j = 1:w
            for n = 1:k
                dif_r = abs(pic(i, j, 1) – colorbar(n, 10, 1));
                dif_g = abs(pic(i, j, 2) – colorbar(n, 10, 2));
                dif_b = abs(pic(i, j, 3) – colorbar(n, 10, 3));
                d = dif_r + dif_g + dif_b;
                if d < min
                pict(i, j) = t(n, 1);
                end
            end
        end
    end

    filename = sprintf(‘frame %d.xlsx’, num);
    writematrix(pict, filename);
end

Answer 1

You should index using [] not (). So colorbar[n,10,1] for example.

However, there are easier ways of subtracting images than going through each pixel for example using cv2.subtract