如何在OpenCV中用另一个RGB值替换某个RGB值的所有像素

Question

我需要能够在 OpenCV 中用另一种颜色替换所有具有特定 RGB 值的像素。

我尝试了一些解决方案，但没有一个对我有用。

实现这一目标的最佳方法是什么？

Answer 1

TLDR;使用 Numpy 将所有绿色像素变为白色：

import numpy as np

pixels[np.all(pixels == (0, 255, 0), axis=-1)] = (255,255,255)

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我在这里做了一些改变颜色的其他方法的例子。首先，我将使用此图像介绍您在问题中提出的确切、特定的 RGB 值。它在左边有三个大块，分别是红色、绿色和蓝色，右边是这些颜色之间的三个渐变：

这是上面的初步答案：

#!/usr/bin/env python3

import cv2
import numpy as np

# Load image
im = cv2.imread('image.png')

# Make all perfectly green pixels white
im[np.all(im == (0, 255, 0), axis=-1)] = (255,255,255)

# Save result
cv2.imwrite('result1.png',im)

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这次我定义颜色名称是为了增加可读性和可维护性。最后一行是重点：

# Define some colours for readability - these are in OpenCV **BGR** order - reverse them for PIL
red   = [0,0,255]
green = [0,255,0]
blue  = [255,0,0]
white = [255,255,255]
black = [0,0,0]

# Make all perfectly green pixels white
im[np.all(im == green, axis=-1)] = white

同样的结果。

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这次我制作了一个可重复使用的红色像素蒙版，可以在后续操作中使用。分配im[Rmask] = black 的最后一行现在特别容易阅读：

# Define some colours for readability - these are in OpenCV **BGR** order - reverse them for PIL
red   = [0,0,255]
green = [0,255,0]
blue  = [255,0,0]
white = [255,255,255]
black = [0,0,0]

# Make mask of all perfectly red pixels
Rmask = np.all(im == red, axis=-1)

# Make all red pixels black
im[Rmask] = black

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这一次我结合一个红色和蓝色像素的蒙版，这样你就可以看到蒙版的威力。最后一行是重点：

# Define some colours for readability - these are in OpenCV **BGR** order - reverse them for PIL
red   = [0,0,255]
green = [0,255,0]
blue  = [255,0,0]
white = [255,255,255]
black = [0,0,0]

# Make mask of all perfectly red pixels and all perfectly blue pixels
Rmask = np.all(im == red,  axis=-1)
Bmask = np.all(im == blue, axis=-1)

# Make all red or blue pixels black
im[Rmask | Bmask] = black

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这次我将所有非红色像素变为黑色 - 希望您现在正在欣赏蒙版的威力。最后一行是重点：

# Define some colours for readability - these are in OpenCV **BGR** order - reverse them for PIL
red   = [0,0,255]
green = [0,255,0]
blue  = [255,0,0]
white = [255,255,255]
black = [0,0,0]

# Make mask of all perfectly red pixels
Rmask = np.all(im == red,  axis=-1)

# Make all non-red pixels black
im[~Rmask] = black

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到目前为止，我们只将一些像素选择为一种新颜色。如果我们想在一次通过中使一些像素成为一种颜色，而让所有其他像素成为不同的颜色怎么办？最后一行是重点：

# Define some colours for readability - these are in OpenCV **BGR** order - reverse them for PIL
red   = [0,0,255]
green = [0,255,0]
blue  = [255,0,0]
white = [255,255,255]
black = [0,0,0]

# Make mask of all perfectly red pixels
Rmask = np.all(im == red,  axis=-1)

# Make all red pixels white AND at same time everything else black
im = np.where(np.all(im == red, axis=-1, keepdims=True), white, black)

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如果您想影响整个范围的颜色，而不是特定的 RGB 值，请查看 here 和 here。

关键字：图像处理、Python、prime、change colour、change color、prime。