How the displayed value is calculated?

I want to analyze an image numerically. The displayed result is different from the output of OpenCV/cvkit.

Take the first-pixel(top-left) value, when check in cvkit with: sv ORTHO_ColorN_01_Z000_PRO.png, and point to the top-left, the result is (126, 131, 254) and is consistent with the first print(). After gammaCorrection and divided by 255, the value is (0.21176471, 0.22745098, 0.98823529), but the displaied value is (0.2086, 0.2270, 0.9911).

Since the image is a normal maps(or in other formats such as depth maps), the accuracy of the values is critical. So we hope tev can add the ability to display raw value.

CODE:

import cv2
import numpy as np

def gammaCorrectionDecoding(src, gamma):
    """
    NOTE: https://stackoverflow.com/a/16521337/10636347
        Gamma decoding is used to restore the original values, so the formula for that is:
        original = ((encoded / 255) ^ gamma) * 255
    """
    table = [((i / 255) ** gamma) * 255 for i in range(256)]
    table = np.array(table, np.uint8)
    return cv2.LUT(src, table)

path_img = "/home/lab9/Videos/for_tev/ORTHO_ColorN_01_Z000_PRO.png"
img = cv2.imread(path_img, -1)
img = cv2.cvtColor(img, cv2.COLOR_BGR2RGB)
img = img[1082:1084, 990:993]
print(img)
img = gammaCorrectionDecoding(img, 2.2)
img = img / 255.0
print(img)

RES:

>>> [[[126 131 254]
  [127 131 254]
  [128 131 254]]

 [[123 126 254]
  [123 127 254]
  [122 127 254]]]

>>> [[[0.21176471 0.22745098 0.98823529]
  [0.21568627 0.22745098 0.98823529]
  [0.21568627 0.22745098 0.98823529]]

 [[0.2        0.21176471 0.98823529]
  [0.2        0.21568627 0.98823529]
  [0.19607843 0.21568627 0.98823529]]]

ORTHO_ColorN_01_Z000_PRO tmp

Tom94 / tev

How the displayed value is calculated? #149