python - 将 openCV 查找表 (LUT) 应用于图像

我想在图像上应用自定义颜色查找表 ( LUT )。

我查看了 openCV LUT Api 但我似乎无法正确理解。

#!/bin/bash
# -*- coding: utf-8 -*-

import os
import numpy as np
import cv2

b_max = 230
g_max = 220
r_max = 250

identity = np.arange(256, dtype = np.dtype('uint8'))

b_channel = np.arange(b_max, dtype = np.dtype('uint8'))
b_channel = np.append(b_channel, (256-b_max)*[b_max])
g_channel = np.arange(g_max, dtype = np.dtype('uint8'))
g_channel = np.append(g_channel, (256-g_max)*[g_max])
r_channel = np.arange(r_max, dtype = np.dtype('uint8'))
r_channel = np.append(r_channel, (256-r_max)*[r_max])

if 256 != b_channel.size or 256 != g_channel.size or 256 != r_channel.size:
    print "size of arrays don't match!"

lut = np.dstack((identity, identity, b_channel, g_channel, r_channel))

# Load the image
img = cv2.imread('input.jpg',cv2.IMREAD_COLOR)
dstImage = cv2.LUT(img, lut)
cv2.imwrite('output.jpg', dstImage)

我收到以下错误:

OpenCV Error: Assertion failed ((lutcn == cn || lutcn == 1) && _lut.total() == 256 && _lut.isContinuous() && (depth == CV_8U || depth == CV_8S)) in cv::LUT, file C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\core\src\convert.cpp, line 5690
Traceback (most recent call last):
  File "ApplyCLUT.py", line 33, in <module>
    dstImage = cv2.LUT(img, lut)
cv2.error: C:\build\master_winpack-bindings-win32-vc14-static\opencv\modules\core\src\convert.cpp:5690: error: (-215) (lutcn == cn || lutcn == 1) && _lut.total() == 256 && _lut.isContinuous() && (depth == CV_8U || depth == CV_8S) in function cv::LUT

编辑:
更改为此行:

lut = np.dstack( (b_channel, g_channel, r_channel) )

它会起作用!

最佳答案

下面是构建 LUT 的示例:

identity = np.arange(256, dtype = np.dtype('uint8'))
zeros = np.zeros(256, np.dtype('uint8'))
lut = np.dstack((identity, identity, zeros))

请注意，有更简单直接的方法将红色 channel 归零:

img[:,:,2] = 0

同样调用 LUT 函数应该如下所示:

dstImage = cv2.LUT(img, lut)

将大于 b_max 的蓝色值设置为 b_max:

b_max = 20
img[img[:,:,0] > b_max, 0] = b_max;

关于python - 将 openCV 查找表 (LUT) 应用于图像，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/42169247/