反转图像在Python与OpenCV的 [英] inverting image in Python with OpenCV

问题描述

欲加载彩色图像，将其转换为灰度，然后在该文件中反转数据。

I want to load a color image, convert it to grayscale, and then invert the data in the file.

我需要：遍历在OpenCV的阵列上，并与这个公式改变每一个值（它可能是错误的，但对我来说似乎是合理的）：

What I need: to iterate over the array in OpenCV and change every single value with this formula (it might be wrong but it seems reasonable for me):

img[x,y] = abs(img[x,y] - 255)

但我不明白为什么没有它的工作原理：

but I don't understand why doesn't it works:

def inverte(imagem, name):
    imagem = abs(imagem - 255)
    cv2.imwrite(name, imagem)


def inverte2(imagem, name):
    for x in np.nditer(imagem, op_flags=['readwrite']):
        x = abs(x - 255)
    cv2.imwrite(name, imagem)


if __name__ == '__main__':
    nome = str(sys.argv[1])
    image = cv2.imread(nome)
    gs_imagem = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    inverte(gs_imagem, "invertida.png")
    inverte2(gs_imagem, "invertida2.png")

我不想做一个明确的循环（我想是更Python）。我可以看到，在得到了一个白色背景原来黑色的形象，但仅此并不看起来像其他的颜色有很多（如果有的话）的变化。

I don't want to do an explicit loop (I am trying to be more pythonic). I can see that in one image that got a white background it turned black, but only this it doesn't looks like the other colors are having much (if any) change.

推荐答案

您几乎做到了。你被事实欺骗了 ABS（IMAGEM-255）会给，因为你的 DTYPE 是一个无符号的一个错误的结果整数。你要做的（255 IMAGEM）以保持整数符号：

You almost did it. You were tricked by the fact that abs(imagem-255) will give a wrong result since your dtype is an unsigned integer. You have to do (255-imagem) in order to keep the integers unsigned:

def inverte(imagem, name):
    imagem = (255-imagem)
    cv2.imwrite(name, imagem)

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