计算机视觉: 实验一

代码地址：Github

实验要求

任意找一张彩色图像，完成以下任务:

  • 写代码转化为灰度图，然后保存为 .png 格式；
  • 写代码将彩色图统— resize 为 224x224 大小，然后保存为 .tif 格式;
  • 写代码实现 RGB 到 HIS 色彩空间的转化，通过 matplot 可视化原始图像，H图像、I 图像和 S 图像

实验过程

原图:

SnowGirl

问题一

import cv2
import matplotlib.pyplot as plt

# 使用cv2库读取图像然后保存为灰度图像
img = cv2.imread('./img/SnowGirl.jpg', cv2.IMREAD_GRAYSCALE)
cv2.imwrite('./result/gray_SnowGirl.jpg', img)

plt.imshow(img, cmap='gray')
plt.axis('off')
plt.show()

运行代码后生成如下文件:

image-20230307165033728

问题二

import PIL.Image as Image
import matplotlib.pyplot as plt

# 使用 PIL 读入图片
img = Image.open('./img/SnowGirl.jpg')

# 改变图片 size
img_resize = img.resize((224, 224))
img_resize.save('./result/SnowGirl.tif')

plt.imshow(img_resize)
plt.axis('off')
plt.show()

运行代码后生成如下文件:

image-20230307165047936

问题三

import cv2
import numpy as np
from matplotlib import pyplot as plt


def rgbtohsi(rgb_lwpImg):
    rows = int(rgb_lwpImg.shape[0])
    cols = int(rgb_lwpImg.shape[1])
    b, g, r = cv2.split(rgb_lwpImg)
    # 归一化到[0,1]
    b = b / 255.0
    g = g / 255.0
    r = r / 255.0
    hsi_lwpImg = rgb_lwpImg.copy()
    for i in range(rows):
        for j in range(cols):
            num = 0.5 * ((r[i, j] - g[i, j]) + (r[i, j] - b[i, j]))
            den = np.sqrt((r[i, j] - g[i, j]) ** 2 + (r[i, j] - b[i, j]) * (g[i, j] - b[i, j]))
            theta = float(np.arccos(num / den))

            if den == 0:
                H = 0
            elif b[i, j] <= g[i, j]:
                H = theta
            else:
                H = 2 * 3.14169265 - theta

            min_RGB = min(min(b[i, j], g[i, j]), r[i, j])
            sum = b[i, j] + g[i, j] + r[i, j]
            if sum == 0:
                S = 0
            else:
                S = 1 - 3 * min_RGB / sum

            H = H / (2 * 3.14159265)
            I = sum / 3.0
            # 输出HSI图像，扩充到255以方便显示，一般H分量在[0,2pi]之间，S和I在[0,1]之间
            hsi_lwpImg[i, j, 0] = H * 255
            hsi_lwpImg[i, j, 1] = S * 255
            hsi_lwpImg[i, j, 2] = I * 255
    return hsi_lwpImg


if __name__ == '__main__':
    rgb_lwpImg = cv2.imread("./img/SnowGirl.jpg")
    hsi_lwpImg = rgbtohsi(rgb_lwpImg)

    img_H = hsi_lwpImg * [1, 0, 0]
    img_S = hsi_lwpImg * [0, 1, 0]
    img_I = hsi_lwpImg * [0, 0, 1]

    plt.subplot(2, 3, 1)
    plt.imshow(rgb_lwpImg[..., ::-1])
    plt.axis('off')
    plt.subplot(2, 3, 2)
    plt.imshow(hsi_lwpImg)
    plt.axis('off')
    plt.subplot(2, 3, 3)
    plt.imshow(img_H)
    plt.axis('off')
    plt.subplot(2, 3, 4)
    plt.imshow(img_S)
    plt.axis('off')
    plt.subplot(2, 3, 5)
    plt.imshow(img_I)
    plt.axis('off')
    plt.show()

运行代码后生成如下文件:

image-20230307165107170