画histogram的wand cv2 方法对比 | 图像工程师的笔记

type

Post

status

Published

date

Mar 12, 2023 02:58 AM

slug

summary

category

技术折腾

icon

fas fa-trophy-alt

password

首先, 用wand 我还不会优雅的画histogram

如下, 因为img.histogram 是iter 类型, 没对应的items 输出.

My guess is that the function used to build the dict keys in __iter__ (PixelGetColorAsString ) is not the same as the one used in __getitem__ (PixelGetColorAsNormalizedString ).


import requests, os, cv2, random, wand, pyexiv2
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
from wand.image import Image
from wand.display import display

with Image(filename='images/lena.jpg') as original:  # 330, 252
    img = original.clone()
    img.transform_colorspace('gray')
    # with img.channel_images['red'] as red_image:
    # plt.imshow(img, cmap='gray')

    # 不加cmap 的话, 图片异常
    # plt.imshow(img)

    # 不加这句, py文件不显示图片
    # plt.show()

    plt.plot(img.histogram.items())
    plt.show()

用cv2 就很简单了


import cv2
import matplotlib.pyplot as plt

image = cv2.imread('images/lena.jpg', cv2.IMREAD_COLOR)
image_gray = cv2.imread('images/lena.jpg', cv2.IMREAD_GRAYSCALE)

histb = cv2.calcHist([image], [0], None, [256], [0, 255])
histg = cv2.calcHist([image], [1], None, [256], [0, 255])
histr = cv2.calcHist([image], [2], None, [256], [0, 255])
hist_gray = cv2.calcHist([image_gray], [0], None, [256], [0, 255])


plt.plot(histb, color='b')
plt.plot(histg, color='g')
plt.plot(histr, color='r')
plt.plot(hist_gray, color='black')

plt.show()

但出的图是下面这样:

没有像ps这样的效果,

这个在plt中不知叫什么效果?