使用PIL（Python）在jpeg图像中找到给定的RGB值？

Question

Now I read a jpeg image using PIL, get the values of RGB.

Although I can combine all the RGBs and then find the width and height that equal to the given value of rgb.

Is there any more effective method or function achieve this goal?

My ultimate goal is to get data of dBZ on this image, including latitude and longitude information.

So first step, I need to get coordinates in image equal to the given RGB.

Answer 1

Using NumPy's argwhere is a straightforward way to achieve what you want. For example, you could obtain the spatial coordinates of those pixels with RGB values [105, 171, 192] like this:

In [118]: from skimage import io

In [119]: import numpy as np

In [120]: img = io.imread('https://i.stack.imgur.com/EuHas.png')

In [121]: ref = [105, 171, 192] 

In [122]: indices = np.argwhere(np.all(img == ref, axis=-1))

In [123]: indices
Out[123]: 
array([[ 71, 577],
       [ 79, 376],
       [ 79, 386],
       [ 95, 404]], dtype=int64)

The following snippet makes it apparent that the results above are correct:

import matplotlib.pyplot as plt

fig, (ax1, ax2) = plt.subplots(1, 2)

ax1.imshow(img)
ax1.set_title('Original map')
ax1.set_axis_off()

ax2.imshow(img)
ax2.set_title('Pixels with RGB = ' + str(ref))
for y, x in indices:
    ax2.add_artist(plt.Circle((x, y), 8, color='r'))