OpenCV的等高线画法

布满荆棘的人生 2022-06-08 02:48 439阅读 0赞

用于圈出图片上颜色深浅不同的区域

处理步骤：gray + threshold + open + distanceTransform + medianBlur + find\_contours

from skimage import io,color
    import numpy as np
    import cv2
    from matplotlib import pyplot as plt
    from IPython.display import display
    from ipywidgets import interact,interactive,fixed
    plt.style.use('classic')

1.读取图片，并二值化

![原始图片img][img]

![通道转换后的图片img2][img2]

img = io.imread('img.JPG')
    img2 = io.imread('img2.JPG')
    
    gray = cv2.cvtColor(img2,cv2.COLOR_BGR2GRAY)
    # ret 值多凭感觉
    thresh = np.ones_like(gray)
    ret = 168
    thresh[gray < ret] = 255
    thresh[gray > ret] = 0
    
    fig = plt.figure(figsize=(16, 6))
    plt.subplot(131),plt.imshow(img)
    plt.subplot(132),plt.imshow(gray,'gray')
    plt.subplot(133),plt.imshow(thresh,'gray')
    plt.show()

![原图-灰度图-二值化图][-_-]

2.降噪，扩张并获得距离参数

# noise removal
    kernel = np.ones((3,3),np.uint8)
    opening = cv2.morphologyEx(thresh,cv2.MORPH_OPEN,kernel, iterations = 2)
    
    # sure background area
    sure_bg = cv2.dilate(opening,kernel,iterations=3)
    
    # Finding sure foreground area
    dist_transform = cv2.distanceTransform(opening,cv2.DIST_L2,5)
    
    # distanceTransform
    fig = plt.figure(figsize=(16, 6))
    plt.subplot(131),plt.imshow(opening,'gray')
    plt.subplot(132),plt.imshow(sure_bg,'gray')
    plt.subplot(133),plt.imshow(dist_transform,'gray')
    
    plt.show()

![1240][]

3.滑动调节等高线高度，绘制等高线

def distance(dist_transform,thresh=0.1):
        ret, sure_fg = cv2.threshold(dist_transform,thresh*dist_transform.max(),255,0)
        sure_fg = np.uint8(sure_fg)
        median_img = cv2.medianBlur(sure_fg,17)
        fig = plt.figure(figsize=(20,18))
        plt.subplot(121),plt.imshow(median_img,'gray'),plt.xticks([]),plt.yticks([])
    
        im2, contours, hierarchy = cv2.findContours(median_img, cv2.RETR_TREE, cv2.CHAIN_APPROX_SIMPLE)
        img_ground = img2.copy()
        cv2.drawContours(img_ground,contours,-1,(0,255,225),5)
    
        plt.subplot(122),plt.imshow(img_ground),plt.xticks([]),plt.yticks([])
        plt.show()
    
        return median_img,img_ground
    
    lims = (0.0,1.0,0.05)
    w = interactive(distance,dist_transform = fixed(dist_transform),thresh = lims)
    display(w)

可以拖动进度条调整阈值，以改变等高线位置

![效果图][1240 1]

[img]: /images/20220608/b55e682b63fc4768aecc00a784355b0f.png
[img2]: /images/20220608/60bbf68519f0431faa4a00d7542ad99f.png
[-_-]: /images/20220608/9e4d450ca5314cf792f8f752526211bd.png
[1240]: /images/20220608/d569cf776a834cf48aa0cfcd05b4577f.png
[1240 1]: /images/20220608/f442301cd8854bcdaaddb011a0253b18.png