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OpenCV-Python 绘制人脸 Delaunay 三角剖

OpenCV-Python 绘制人脸 Delaunay 三角剖

作者: 小张Python | 来源:发表于2020-06-15 18:05 被阅读0次

    1,介绍

    开始之前,向大家提前说声抱歉,上一篇文章末尾提到了,在这篇文章将给大家介绍关于用 OpenCV 实现人脸融合技术,由于人脸融合技术所需的知识储备有点多,不只是之前介绍的的特征点提取,还有本文所提到的三角剖分,因此文章会向后面推迟一点,但请大家放心,人脸融合技术一定会在随后的几篇文章安排上日程。

    看到标题里的两个词 Delaunay 三角剖分 和 Voronoi,估计第一次见到的小伙伴可能一脸懵(说的就是我自己),为了更直观地认识这两个概念,请看下图:

    左图:68个人脸特征点 中图:Delaunay 三角剖分,右图 Voronoi 图表

    左图是上篇文章提到的 68个人脸特征点标记,中图是基于左图的基础上对 68个点进行 点与点之间形成 Delaunay 三角剖分(德劳内),左图是基于中间图绘制的的 Voronoi Diagram (沃罗诺伊图)

    2,Delaunay 三角剖分

    Delaunay 三角剖分算法命名那个来源于俄国数学家 Boris Delaunay,该方法目的是最大化三角剖分中三角形中最小角,目的是避免“极瘦“的三角形的出现

    Snipaste_2020-06-04_15-23-46.png

    上方左图与右图的变换站示的就是 Delaunay 怎样最大化最小角,左右两图是对于四个顶点的两种不同的剖分方式;但左图中 顶点 A、C 不在三角形 BCD、ABD 的外接圆内,使得 角 C 非常大

    右图对剖分形式有两个方的 改动:1,B、D 坐标右移;2,剖分线由 BD 变为 AC ;最后使得剖分后的三角形不那么”瘦“

    3,Voronoi Diagram

    Voronoi 命名同样也是来源于一个 俄国数学家 Georgy Voronoy,有趣的是 Georgy Voronoy 是 Boris Delaunay 的博士导师

    Voronoi 图是基于 Delaunay 三角剖分创建,取 Delaunay 剖分的所有顶点,用线段连接相邻三角形的外接圆心,构成一个区域,相邻不同区域用不同颜色覆盖;Voronoi 图目前常用于凸边形区域分割领域

    从下面20个顶点组成的 Voronoi 图种可以了解到,图中相邻点与点之间的距离是等长的

    20个顶点构成的 Voronoi

    4,OpenCV 代码实现

    1,首先需要获取人脸 68 个特征点坐标,并写入 txt 文件,方便后面使用,这里会用到的代码

    import dlib
    import cv2
    
    predictor_path  = "E:/data_ceshi/shape_predictor_68_face_landmarks.dat"
    png_path = "E:/data_ceshi/timg.jpg"
    
    txt_path = "E:/data_ceshi/points.txt"
    f = open(txt_path,'w+')
    
    
    detector = dlib.get_frontal_face_detector()
    #相撞
    predicator = dlib.shape_predictor(predictor_path)
    win = dlib.image_window()
    img1 = cv2.imread(png_path)
    
    
    dets = detector(img1,1)
    print("Number of faces detected : {}".format(len(dets)))
    for k,d in enumerate(dets):
        print("Detection {}  left:{}  Top: {} Right {}  Bottom {}".format(
            k,d.left(),d.top(),d.right(),d.bottom()
        ))
        lanmarks = [[p.x,p.y] for p in predicator(img1,d).parts()]
        for idx,point in enumerate(lanmarks):
            f.write(str(point[0]))
            f.write("\t")
            f.write(str(point[1]))
            f.write('\n')
    

    写入后,txt 中格式如下

    image

    2,利用图像大小创建一个矩形范围( 因为脸部特征点都是图中),创建一个 Subdiv2D 实例(后面两个图的绘制都会用到这个类),把点都插入创建的类中:

     #Create an instance of Subdiv2d
        subdiv = cv2.Subdiv2D(rect)
        #Create an array of points
        points = []
        #Read in the points from a text file
        with open("E:/data_ceshi/points.txt") as file:
            for line in file:
                x,y = line.split()
                points.append((int(x),int(y)))
        #Insert points into subdiv
        for p in points:
            subdiv.insert(p)
    

    3,在原图上绘制 Delaunay 三角剖分并预览,这里我加入了动画效果 — 逐线段绘制(用了 for 循环)

    #Draw delaunay triangles
    def draw_delaunay(img,subdiv,delaunay_color):
        trangleList = subdiv.getTriangleList()
        size = img.shape
        r = (0,0,size[1],size[0])
        for t in  trangleList:
            pt1 = (t[0],t[1])
            pt2 = (t[2],t[3])
            pt3 = (t[4],t[5])
            if (rect_contains(r,pt1) and rect_contains(r,pt2) and rect_contains(r,pt3)):
                cv2.line(img,pt1,pt2,delaunay_color,1)
                cv2.line(img,pt2,pt3,delaunay_color,1)
                cv2.line(img,pt3,pt1,delaunay_color,1)
                
     #Insert points into subdiv
        for p in points:
            subdiv.insert(p)
    
            #Show animate
            if animate:
                img_copy = img_orig.copy()
                #Draw delaunay triangles
                draw_delaunay(img_copy,subdiv,(255,255,255))
                cv2.imshow(win_delaunary,img_copy)
                cv2.waitKey(100)
    

    预览效果如下:

    imag11252323.gif

    4,最后绘制 Voronoi Diagram

     def draw_voronoi(img,subdiv):
        (facets,centers) = subdiv.getVoronoiFacetList([])
    
        for i in range(0,len(facets)):
            ifacet_arr = []
            for f in facets[i]:
                ifacet_arr.append(f)
    
            ifacet = np.array(ifacet_arr,np.int)
            color = (random.randint(0,255),random.randint(0,255),random.randint(0,255))
            cv2.fillConvexPoly(img,ifacet,color)
            ifacets = np.array([ifacet])
            cv2.polylines(img,ifacets,True,(0,0,0),1)
            cv2.circle(img,(centers[i][0],centers[i][1]),3,(0,0,0))
        
      for p in points:
            draw_point(img,p,(0,0,255))
    
      #Allocate space for Voroni Diagram
      img_voronoi = np.zeros(img.shape,dtype = img.dtype)
    
      #Draw Voonoi diagram
      draw_voronoi(img_voronoi,subdiv)
    
    Snipaste_2020-06-04_14-43-10.png
    4,小总结

    Delaunay 三角剖分对于第一次接触的小伙伴来说可能还未完全理解,但这一剖分技术对于做人脸识别、融合、换脸是不可或缺的,本篇文章只是仅通过 OpenCV 的 Subdiv2D 函数下实现此功能,真正的识别技术要比这个复杂地多。

    对于感兴趣的小伙伴们,我的建议还是跟着提供的代码敲一遍,完整代码贴在下面:

    import cv2
    import numpy as np
    import random
    
    #Check if a point is insied a rectangle
    def rect_contains(rect,point):
        if point[0] <rect[0]:
            return False
        elif point[1]<rect[1]:
            return  False
        elif point[0]>rect[2]:
            return False
        elif point[1] >rect[3]:
            return False
        return True
    
    # Draw a point
    def draw_point(img,p,color):
        cv2.circle(img,p,2,color)
    
    #Draw delaunay triangles
    def draw_delaunay(img,subdiv,delaunay_color):
        trangleList = subdiv.getTriangleList()
        size = img.shape
        r = (0,0,size[1],size[0])
        for t in  trangleList:
            pt1 = (t[0],t[1])
            pt2 = (t[2],t[3])
            pt3 = (t[4],t[5])
            if (rect_contains(r,pt1) and rect_contains(r,pt2) and rect_contains(r,pt3)):
                cv2.line(img,pt1,pt2,delaunay_color,1)
                cv2.line(img,pt2,pt3,delaunay_color,1)
                cv2.line(img,pt3,pt1,delaunay_color,1)
    
    # Draw voronoi diagram
    def draw_voronoi(img,subdiv):
        (facets,centers) = subdiv.getVoronoiFacetList([])
    
        for i in range(0,len(facets)):
            ifacet_arr = []
            for f in facets[i]:
                ifacet_arr.append(f)
    
            ifacet = np.array(ifacet_arr,np.int)
            color = (random.randint(0,255),random.randint(0,255),random.randint(0,255))
            cv2.fillConvexPoly(img,ifacet,color)
            ifacets = np.array([ifacet])
            cv2.polylines(img,ifacets,True,(0,0,0),1)
            cv2.circle(img,(centers[i][0],centers[i][1]),3,(0,0,0))
    
    
    if __name__ == '__main__':
        #Define window names;
        win_delaunary = "Delaunay Triangulation"
        win_voronoi = "Voronoi Diagram"
    
        #Turn on animations while drawing triangles
        animate = True
    
        #Define colors for drawing
        delaunary_color = (255,255,255)
        points_color = (0,0,255)
    
        #Read in the image
        img_path = "E:/data_ceshi/timg.jpg"
    
        img = cv2.imread(img_path)
    
        #Keep a copy   around
        img_orig = img.copy()
    
        #Rectangle to be used with Subdiv2D
        size = img.shape
        rect = (0,0,size[1],size[0])
    
        #Create an instance of Subdiv2d
        subdiv = cv2.Subdiv2D(rect)
        #Create an array of points
        points = []
        #Read in the points from a text file
        with open("E:/data_ceshi/points.txt") as file:
            for line in file:
                x,y = line.split()
                points.append((int(x),int(y)))
        #Insert points into subdiv
        for p in points:
            subdiv.insert(p)
    
            #Show animate
            if animate:
                img_copy = img_orig.copy()
                #Draw delaunay triangles
                draw_delaunay(img_copy,subdiv,(255,255,255))
                cv2.imshow(win_delaunary,img_copy)
                cv2.waitKey(100)
    
        #Draw delaunary triangles
        draw_delaunay(img,subdiv,(255,255,255))
    
        #Draw points
        for p in points:
            draw_point(img,p,(0,0,255))
    
        #Allocate space for Voroni Diagram
        img_voronoi = np.zeros(img.shape,dtype = img.dtype)
    
        #Draw Voonoi diagram
        draw_voronoi(img_voronoi,subdiv)
    
        #Show results
        cv2.imshow(win_delaunary,img)
        cv2.imshow(win_voronoi,img_voronoi)
        cv2.waitKey(0)
    
    

    参考链接

    https://www.learnopencv.com/

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