python实现gimp里面的曝光算法

在gimp里面有曝光的功能

 简单看了一下源码，看起来比较简单，使用python简单的实现了一下：

import numpy as np
import cv2


def exposure(img_input, black_level=0, exposure_negated=0.0):
    img_input = img_input.astype(np.float32)
    assert -0.1 <= black_level <= 0.1
    assert -10.0 <= exposure_negated <= 10.0
    white = pow(2, -exposure_negated)
    diff = max(white - black_level, 0.000001)
    gain = 1.0 / diff
    img_output = (img_input - black_level)*gain
    return img_output


if __name__ == '__main__':
    img = cv2.imread('tmp/50.jpg')
    exposure_negateds = [-2.5, -1.0, -0.5, 0.5, 1.0, 2.5]
    for exposure_negated in exposure_negateds:
        res_out = exposure(img, black_level=0, exposure_negated=exposure_negated)
        cv2.imwrite('tmp/50_exposure_{}.jpg'.format(exposure_negated), res_out)

 原图

 0.5曝光

-0.5曝光

 1.0曝光

-1.0曝光

 2.5曝光

 -2.5曝光