图片P模式 PIL 分割

• 最近在做图像分割的时候接触到了图像的P模式，因为给出的mask图片（y_true）为P模式
• P代表palette，调色板，也就是图片中会包含一个调色表的列表，每一个像素位置放的只是一个index，那么这个像素要展示的颜色就是调色板中第index位置展示的颜色
• 我用到的图片显示出的palette是768长度，也就是256 * 3， 因为每个颜色需要RGB三个通道，所以768长度也就对应了256种颜色，这种图片最多能展示256中颜色，而传统的RGB最多可以展示256256256种颜色
• 代码展示会很清楚

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)
        # 打印图片格式
        print(image.mode)
        if image.mode == 'P':
        	# 获取调色板
            palette = image.getpalette()
            print(len(palette))   # 768 = 256 * 3
            print(image.getpalette())
        # 统计每种颜色出现的频率
        print(Counter(np.array(image).flatten()))

output

# 这就是调色板的数据  3个数据为一组，一共256组
[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]

# 这是图片本身的数据颜色统计, 	不是palette的数据
Counter({0: 138158, 20: 25087, 255: 12199, 15: 9895, 9: 2161})