python-opencv image processing basics (eight) image pyramid

image pyramid

reduce=高斯模糊+降采样      PyrDown
expand=扩大+卷积           PyrUp还原

Gaussian Pyramid
Laplacian Pyramid

import cv2 as cv
import numpy as np

#图像金字塔reduce过程
def pyramid_demo(image):
    level = 3
    temp = image.copy()
    pyramid_images = []
    for i in range(level):
        dst = cv.pyrDown(temp)
        pyramid_images.append(dst)
        cv.imshow("pyramid_down_"+str(i), dst)
        temp = dst.copy()
    return pyramid_images

#图像expend过程和原图相减 得到拉普拉斯金字塔
def lapalian_demo(image):
    pyramid_images = pyramid_demo(image)
    level = len(pyramid_images)
    for i in range(level-1, -1, -1):#从高到低 递减 从低分辨率到高分辨率 还原图像
        if (i-1) < 0 :
            expand = cv.pyrUp(pyramid_images[i], dstsize=image.shape[:2])
            lpls = cv.subtract(image, expand)
            cv.imshow("lapalian_down_" + str(i), lpls)
        else:
            expand = cv.pyrUp(pyramid_images[i], dstsize=pyramid_images[i-1].shape[:2])
            lpls = cv.subtract(pyramid_images[i-1], expand)
            cv.imshow("lapalian_down_"+str(i), lpls)

if __name__=='__main__':
    print("--------- Python OpenCV Tutorial ---------")
    src = cv.imread("../opencv-python-img/lena.png")#图像大小是2的倍数不然会出错。
    cv.namedWindow("input image", cv.WINDOW_AUTOSIZE)
    cv.imshow("input image", src)
    #pyramid_demo(src)
    lapalian_demo(src)
    cv.waitKey(0)

    cv.destroyAllWindows()