DPI -OPENCV

import cv2 as cv
import numpy as np

def gammaFilter(img, parameterValue=1.5):
    values = np.array([((i / 255.0) ** (1.0 / parameterValue)) * 255
                      for i in np.arange(0, 256)]).astype("uint8")
    result =  cv.LUT(img, values)
    return result

def addLabel(img, text, positionX):
    cv.putText(img, text, (positionX, 50), cv.FONT_HERSHEY_SIMPLEX, 1, (255, 255, 255), 2)

def getHistogram(img):
    grayImg = cv.cvtColor(img, cv.COLOR_BGR2YUV)
    grayImg[:, :, 0] = cv.equalizeHist(img[:, :, 0])
    grayImg = cv.cvtColor(img, cv.COLOR_YUV2BGR)

    histogram = cv.calcHist([grayImg], [0], None, [256], [0, 255])
    result = np.zeros((255, 256))
    for x, y in enumerate(histogram):
        cv.line(result, (x, 0), (x, y), (255, 255, 255))

    return result

originalImg = cv.imread("questao.jpeg")

imgFiltered = gammaFilter(originalImg, 1.8)
addLabel(imgFiltered, "Gamma filter", 540)
addLabel(originalImg, "Original Image", 540)

# show original image | show histogram original image |
cv.imshow("DPI - Original image", originalImg)
histogramOriginalImg = getHistogram(originalImg)
cv.imshow("DPI - Histogram - Original Image", histogramOriginalImg)

# show manipuled image based on original image | show histogram after manipuled original image
cv.imshow("DPI - Manipuled Image", imgFiltered)
histogramFilteredGammaImg = getHistogram(imgFiltered)
cv.imshow("Histogram - Filtered Image", histogramFilteredGammaImg)

cv.waitKey()