圖片P模式 PIL 分割

• 最近在做圖像分割的時候接觸到了圖像的P模式，因爲給出的mask圖片（y_true）爲P模式
• P代表palette，調色板，也就是圖片中會包含一個調色表的列表，每一個像素位置放的只是一個index，那麼這個像素要展示的顏色就是調色板中第index位置展示的顏色
• 我用到的圖片顯示出的palette是768長度，也就是256 * 3， 因爲每個顏色需要RGB三個通道，所以768長度也就對應了256種顏色，這種圖片最多能展示256中顏色，而傳統的RGB最多可以展示256256256種顏色
• 代碼展示會很清楚

code

import os
import numpy as np
from PIL import Image
from collections import Counter
from random import shuffle

if __name__ == '__main__':
    root_dir = "/data/mayilong/PycharmProjects/03-04/Keras-FCN/datasets/VOC2012/combined_annotations"
    names = os.listdir(root_dir)
    shuffle(names)
    for name in names:
        path = os.path.join(root_dir, name)
        image = Image.open(path)
        # 打印圖片格式
        print(image.mode)
        if image.mode == 'P':
        	# 獲取調色板
            palette = image.getpalette()
            print(len(palette))   # 768 = 256 * 3
            print(image.getpalette())
        # 統計每種顏色出現的頻率
        print(Counter(np.array(image).flatten()))

output

# 這就是調色板的數據  3個數據爲一組，一共256組
[0, 0, 0, 128, 0, 0, 0, 128, 0, 128, 128, 0, 0, 0, 128, 128, 0, 128, 0, 128, 128, 128, 128, 128, 64, 0, 0, 192, 0, 0, 64, 128, 0, 192, 128, 0, 64, 0, 128, 192, 0, 128, 64, 128, 128, 192, 128, 128, 0, 64, 0, 128, 64, 0, 0, 192, 0, 128, 192, 0, 0, 64, 128, 128, 64, 128, 0, 192, 128, 128, 192, 128, 64, 64, 0, 192, 64, 0, 64, 192, 0, 192, 192, 0, 64, 64, 128, 192, 64, 128, 64, 192, 128, 192, 192, 128, 0, 0, 64, 128, 0, 64, 0, 128, 64, 128, 128, 64, 0, 0, 192, 128, 0, 192, 0, 128, 192, 128, 128, 192, 64, 0, 64, 192, 0, 64, 64, 128, 64, 192, 128, 64, 64, 0, 192, 192, 0, 192, 64, 128, 192, 192, 128, 192, 0, 64, 64, 128, 64, 64, 0, 192, 64, 128, 192, 64, 0, 64, 192, 128, 64, 192, 0, 192, 192, 128, 192, 192, 64, 64, 64, 192, 64, 64, 64, 192, 64, 192, 192, 64, 64, 64, 192, 192, 64, 192, 64, 192, 192, 192, 192, 192, 32, 0, 0, 160, 0, 0, 32, 128, 0, 160, 128, 0, 32, 0, 128, 160, 0, 128, 32, 128, 128, 160, 128, 128, 96, 0, 0, 224, 0, 0, 96, 128, 0, 224, 128, 0, 96, 0, 128, 224, 0, 128, 96, 128, 128, 224, 128, 128, 32, 64, 0, 160, 64, 0, 32, 192, 0, 160, 192, 0, 32, 64, 128, 160, 64, 128, 32, 192, 128, 160, 192, 128, 96, 64, 0, 224, 64, 0, 96, 192, 0, 224, 192, 0, 96, 64, 128, 224, 64, 128, 96, 192, 128, 224, 192, 128, 32, 0, 64, 160, 0, 64, 32, 128, 64, 160, 128, 64, 32, 0, 192, 160, 0, 192, 32, 128, 192, 160, 128, 192, 96, 0, 64, 224, 0, 64, 96, 128, 64, 224, 128, 64, 96, 0, 192, 224, 0, 192, 96, 128, 192, 224, 128, 192, 32, 64, 64, 160, 64, 64, 32, 192, 64, 160, 192, 64, 32, 64, 192, 160, 64, 192, 32, 192, 192, 160, 192, 192, 96, 64, 64, 224, 64, 64, 96, 192, 64, 224, 192, 64, 96, 64, 192, 224, 64, 192, 96, 192, 192, 224, 192, 192, 0, 32, 0, 128, 32, 0, 0, 160, 0, 128, 160, 0, 0, 32, 128, 128, 32, 128, 0, 160, 128, 128, 160, 128, 64, 32, 0, 192, 32, 0, 64, 160, 0, 192, 160, 0, 64, 32, 128, 192, 32, 128, 64, 160, 128, 192, 160, 128, 0, 96, 0, 128, 96, 0, 0, 224, 0, 128, 224, 0, 0, 96, 128, 128, 96, 128, 0, 224, 128, 128, 224, 128, 64, 96, 0, 192, 96, 0, 64, 224, 0, 192, 224, 0, 64, 96, 128, 192, 96, 128, 64, 224, 128, 192, 224, 128, 0, 32, 64, 128, 32, 64, 0, 160, 64, 128, 160, 64, 0, 32, 192, 128, 32, 192, 0, 160, 192, 128, 160, 192, 64, 32, 64, 192, 32, 64, 64, 160, 64, 192, 160, 64, 64, 32, 192, 192, 32, 192, 64, 160, 192, 192, 160, 192, 0, 96, 64, 128, 96, 64, 0, 224, 64, 128, 224, 64, 0, 96, 192, 128, 96, 192, 0, 224, 192, 128, 224, 192, 64, 96, 64, 192, 96, 64, 64, 224, 64, 192, 224, 64, 64, 96, 192, 192, 96, 192, 64, 224, 192, 192, 224, 192, 32, 32, 0, 160, 32, 0, 32, 160, 0, 160, 160, 0, 32, 32, 128, 160, 32, 128, 32, 160, 128, 160, 160, 128, 96, 32, 0, 224, 32, 0, 96, 160, 0, 224, 160, 0, 96, 32, 128, 224, 32, 128, 96, 160, 128, 224, 160, 128, 32, 96, 0, 160, 96, 0, 32, 224, 0, 160, 224, 0, 32, 96, 128, 160, 96, 128, 32, 224, 128, 160, 224, 128, 96, 96, 0, 224, 96, 0, 96, 224, 0, 224, 224, 0, 96, 96, 128, 224, 96, 128, 96, 224, 128, 224, 224, 128, 32, 32, 64, 160, 32, 64, 32, 160, 64, 160, 160, 64, 32, 32, 192, 160, 32, 192, 32, 160, 192, 160, 160, 192, 96, 32, 64, 224, 32, 64, 96, 160, 64, 224, 160, 64, 96, 32, 192, 224, 32, 192, 96, 160, 192, 224, 160, 192, 32, 96, 64, 160, 96, 64, 32, 224, 64, 160, 224, 64, 32, 96, 192, 160, 96, 192, 32, 224, 192, 160, 224, 192, 96, 96, 64, 224, 96, 64, 96, 224, 64, 224, 224, 64, 96, 96, 192, 224, 96, 192, 96, 224, 192, 224, 224, 192]

# 這是圖片數據中顏色統計，也就是index的統計
Counter({0: 138158, 20: 25087, 255: 12199, 15: 9895, 9: 2161})