Opencv或Numpy-有效替换图像中的像素列表 [英] Opencv or Numpy-- replace a list of pixels in an image, efficiently

问题描述

您的OpenCV或Numpy Gurus，

我一直在寻找答案，但是很惊讶在这里或其他地方找不到它...

我有一个黑色图像，我想用某个值替换一个像素列表(相当大的列表).将来，某些值"将是值的列表，但是目前，让我们保持简单.

进一步简化，我只在下面使用一个由2个数字组成的二维数组，而不是RGB值... 因此，这种效率很低的方法适用于这种情况:

a = np.zeros((5, 5,1))

for i in np.asarray( ([2,3],[3,4]) ):
       a[i[0], i[1]] = 20

我希望有一种在二维数组上使用np.put的方法，而我不依赖python循环.

现在，我建议我可以使用

a[ ([2,3],[3,4]) = 20

但是，当我在真正的OpenCV问题中使用这种方法时，却发现它不起作用.这种非常低效的方法可以做到:

coords_list = ([3,5],[55,60],[25,90])
black_image =np.zeros((480,640,3))
for i in coords_list:
    black_image[i[1],i[0]] = [255,255,255]

我希望对许多人来说这是一个简单的问题.

谢谢！

解决方案

实际上，您可以直接使用坐标元组索引矩阵:简单的a[([2, 3], [3, 4])] = 20给出与for循环完全相同的结果. /p>

Hi OpenCV or Numpy Gurus,

I've been searching to an answer to this, but I'm surprised to not find it here or elsewhere...

I have a black image, and I want to replace a list of pixels (quite a large list) with a certain value. In the future, the "certain value" will be a list of values, but for the moment, let's keep it simple.

Simplifying even further, I just use a 2-d array of single numbers below, instead of RGB values... So, this fairly inefficient approach works for this sort of thing:

a = np.zeros((5, 5,1))

for i in np.asarray( ([2,3],[3,4]) ):
       a[i[0], i[1]] = 20

I was hoping there was a way to use np.put on a two dimensional array, where I don't rely on a python loop.

Now I had the suggestion that I could use

a[ ([2,3],[3,4]) = 20

However I notice when I use this approach in my real OpenCV problem it does not work. This very inefficient approach does:

coords_list = ([3,5],[55,60],[25,90])
black_image =np.zeros((480,640,3))
for i in coords_list:
    black_image[i[1],i[0]] = [255,255,255]

I expect this is a simple question to many out there.

Thanks!

解决方案

In fact, you can directly use your tuple of coordinates to index your matrix: a simple a[([2, 3], [3, 4])] = 20 gives the exact same result as your for loop here.

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