如何遍历图像的非零值？ - Python

Question

我喜欢在线提取和显示图像主色的功能。为了节省时间，我只想迭代非零像素而不是整个图像。但是，我更改函数的方式会引发错误：

   if row != [0,0,0]:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

修改后的代码如下：

def dominantColor(image) :
    from matplotlib.pyplot import imshow, show
    from scipy.cluster.vq import whiten
    from scipy.cluster.vq import kmeans
    import pandas as pd

r = []
g = []
b = []
for row in image :
    if row != [0,0,0]: #the part I added to the original code
        print(row)
        for temp_r, temp_g, temp_b in row:
            r.append(temp_r)
            g.append(temp_g)
            b.append(temp_b)

image_df = pd.DataFrame({'red': r, 'green': g, 'blue': b})
image_df['scaled_color_red'] = whiten(image_df['red'])
image_df['scaled_color_blue'] = whiten(image_df['blue'])
image_df['scaled_color_green'] = whiten(image_df['green'])

cluster_centers, _ = kmeans(image_df[['scaled_color_red','scaled_color_blue','scaled_color_green']], 3)
dominant_colors = []
red_std, green_std, blue_std = image_df[['red','green','blue']].std()
for cluster_center in cluster_centers:
    red_scaled, green_scaled, blue_scaled = cluster_center
    dominant_colors.append((
        red_scaled * red_std / 255,
        green_scaled * green_std / 255,
        blue_scaled * blue_std / 255
    ))
imshow([dominant_colors])
show()

return dominant_colors

我应该如何更正我的迭代循环以消除错误并使我的图像只有非零值？（注意：图像实际上是 mask * original_image）

Answer 1

如果你想共同比较数组元素，你需要在比较之后添加 .all() 方法。所以 if (row == [0,0,0]).all().

import numpy as np

image = np.array([
    [0, 0, 0],
    [1, 0, 0],
    [0, 0, 1],
])

for row in image:
    if not (row == [0, 0, 0]).all():
        print(row)

结果：

[1 0 0]
[0 0 1]

Answer 2

如果我正确理解你的代码，答案就在你发布的错误日志中：

if row != [0,0,0]:
ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

因此，any 函数检查行中的任何元素是否被评估为真：

for row in image :
    if any(row): #enter the if block if any element is not 0
        print(row)
        for temp_r, temp_g, temp_b in row:
            r.append(temp_r)
            g.append(temp_g)
            b.append(temp_b)

如何遍历图像的非零值？ - Python

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