image - 使用 openCV 在图像中查找特定框

Question

我有以下图片:

我想从中提取显示三角形的框。我使用简单的垂直和水平线检测来做到这一点，在我的机器上总共需要 10 秒。

现在，由于必须多次执行此操作，因此效率非常重要。那么，openCV(或其他任何地方)中是否有任何方法可以有效地提取这些框？在这里，一种比蛮力方法花费更少时间的有效方法就足够了。

感谢任何帮助!

我的方法:

我创建了一个函数 searchHorizo​​ntalLinesX 用于搜索特定长度的行。它通过遍历每个像素一次来实现。我的图片尺寸为:2479 x 3504 = 8686416 像素。 (附加图片质量低，因为上传限制为 2MB。我使用的图片超过 16 MB)

因此，我输入了整个框的宽度 (L1) 和编号为 5 的框的宽度 (L2)。现在，该函数返回具有 L1 长度和 L2 长度的行。因此，所有长度为 L1 的都可以用来提取框 1、2、3、4、6、7、8、9 和 10。

找到这些线后，我会搜索它们之间相差 H 的线，其中 H 是每个框的高度，对于每个框。使用这些我得到了盒子。

对于不是提取的整列的框，我尝试找到一条从顶部到底部的线，然后提取该线相关侧的图像。

def searchHorizontalLinesX(im,lengths,pg,gap=10):
    """
    im: PIL image object of the file
    lengths: list of lengths of lines to recognize
    pg: Page number of the page to take under consideration
    """
    im.seek(pg)
    dimX = im.size[0]
    dimY = im.size[1]
    pix = im.load()
    line = False 
    n = len(lengths) 
    linez = [[] for i in range(0,n)]
    for j in range(0,dimY):
        for i in range(0,dimX):
            if(line):
                if(pix[i,j][0]!=0 or pix[i,j][1]!=255):
                    line = False
                    end = (i-1,j) 
                    for num,l in enumerate(lengths):
                        if(end[0]-start[0]>(l-gap) and end[0]-start[0]<(l+gap)):
                            linez[num].append([start,end])
                elif(start[1]==j-1 and i==0):#End to end line
                    end = (im.size[0],start[1])
                    line = False
                    for i,l in enumerate(lengths):
                        if(end[0]-start[0]>(l-gap) and end[0]-start[0]<(l+gap)):
                            linez[num].append([start,end])
            else:
                if(pix[i,j][0]==0 or pix[i,j][1]==255):
                    start = (i,j) 
                    line = True
    return linez

def searchVerticalLines(im,length,pg,gap=5):
    """
    im: PIL image object of the file
    length: Length of box
    dimX: Width of the page
    dimY: Height of the page
    pg: Page number of the page to take under consideration
    """
    im.seek(pg)
    dimX = im.size[0] 
    dimY = im.size[1]
    pix = im.load()
    line = False
    linez = []
    start = (0,0) 
    end = (0,0) 
    for i in range(0,dimX):
        for j in range(0,dimY):
            if(line):
                if(pix[i,j][0]!=0 or pix[i,j][1]!=255):
                    line = False
                    end = (i,j-1)
                    if(end[1]-start[1]>(length-gap) and end[1]-start[1]<(length+gap)):
                        linez.append([start,end])
                elif(start[0]==i-1 and j==0):
                    line = False
                    end = (start[0],im.size[1])
                    if(end[1]-start[1]>(length-gap) and end[1]-start[1]<(length+gap)):
                        linez.append([start,end])

            else:
                if(pix[i,j][0]==0 or pix[i,j][1]==255):
                    start = (i,j)
                    line = True 
    return linez

def grouping(hor,width):
    """
    Groups similar horizontal lines together.
    hor: List of lines in the format [[(start_x,start_y),(end_x,end_y)],...]
    width: What width can a line have. Takes all the lines inside this list into a group
    Returns: A list of groups. Each group is a list of lines. Each line has the format [(start_x,start_y),(end_x,end_y)]
    """
    horSet = set()
    for i in hor:
        horSet.add((i[0],i[1]))
    group = []
    count = 0 
    for i in hor:
        if (i[0],i[1]) in horSet:
            print("Visiting :"+str(i))
            for j in hor:
                if (j[0],j[1]) in horSet:
                    if(i[0][0]==j[0][0] and i[1][0]==j[1][0] and abs(j[0][1]-i[0][1])<width and abs(j[1][1]-i[1][1])<width):
                        if(len(group)<=count):
                            group.append([j])
                        else:
                            group[count].append(j)
                        horSet.remove((j[0],j[1]))
            count+=1
    return group
def groupingH(ver,width,heightDifference = 2):
    """
    Groups similar vertical lines together.
    hor: List of lines in the format [[(start_x,start_y),(end_x,end_y)],...]
    width: What width can a line have. Takes all the lines inside this list into a group
    Returns: A list of groups. Each group is a list of lines. Each line has the format [(start_x,start_y),(end_x,end_y)]
    """
    verSet = set()
    for i in ver:
        verSet.add((i[0],i[1]))
    group = []
    count = 0 
    for i in ver:
        if (i[0],i[1]) in verSet:
            for j in ver:
                if (abs(i[0][1]-j[0][1])< heightDifference and abs(i[1][1]-j[1][1])< heightDifference and abs(j[0][0]-i[0][0])<width and abs(j[1][0]-i[1][0])<width):
                        if(len(group)<=count):
                            group.append([j])
                        else:
                            group[count].append(j)
                        verSet.remove((j[0],j[1]))
            count+=1
    return group




def boxing(groupList,boxHeight,gap=5,lw=4):
    """
    Given a groupList, it makes a list of coordinates of boxes that have a boxHeight height+-5
    """
    boxCoord = []
    groupSet = set()
    for i in range(len(groupList)):
        groupSet.add(i)
    for i,g in enumerate(groupList):
        if i in groupSet:
            print("On :"+str(i))
            for j,g1 in enumerate(groupList):
                if j in groupSet:
                    print("    Checking :"+str(j))
                    if(g[0][0][0]==g1[0][0][0] and g[0][1][0]==g1[0][1][0] and abs(g[len(g)-1][0][1]-g1[0][0][1])>=boxHeight-gap and abs(g[len(g)-1][0][1]-g1[0][0][1])<boxHeight+gap):
                        groupSet.remove(j)
                        print("        removing :"+str(j))
                        boxCoord.append((g[0][0][0]+lw,min(g[len(g)-1][0][1],g1[0][0][1])+1,g[0][1][0]-lw,max(g[len(g)-1][0][1],g1[0][0][1])-1))
                        break
            groupSet.remove(i)
    return boxCoord

##############################
def getFrontPageBoxes(im,pg,coords,margin=10):
    """
    coords[0]: List of lengths of horizontal lines to be recognized: 0th for box1, 1st for box2+3 (and 4,5,6,7,8,9,10) 
    coords[1]: Height of box 1
    coords[2]: Height of box 2,3
    coords[3]: Height of box 4,5,6,7
    coords[4]: Height of box 8,10
    coords[5]: Height of box 9
    """
    # Box 1: Police station... et cetera.
    t = []
    t1 = t.append(time())
    linez = searchHorizontalLinesX(im,coords[0],0) #0 for box 1 <-- Takes time
    t2 = t.append(time())
    groupForBox1 = grouping(linez[0],4)
    leftUpperCorner = groupForBox1[0][len(groupForBox1[0])-1][0]
    t3 = t.append(time())
    verLinez = searchVerticalLines(im,coords[1],0,10) # <-- Takes time
    t4 = t.append(time())
    rightLowerCorner = verLinez[0][1]
    box1 = im.crop((leftUpperCorner[0]+margin,leftUpperCorner[1]+margin,linez[0][0][1][0]-margin,rightLowerCorner[1]-margin))
    # Box 2+3: Polling station name and address
    groupForBox2 = grouping(linez[1],4)
    bxesFor2 = boxing(groupForBox2,coords[2])
    box2Uncropped = im.crop(bxesFor2[len(bxesFor2)-1]) # The last one is the one we want
    t5 = t.append(time())
    verLinesFor2 = searchVerticalLines(box2Uncropped,box2Uncropped.size[1],0,10) # <-- Takes time
    t6 = t.append(time())
    group2ForBox2 = groupingH(verLinesFor2,4)
    leftUpperCorner = (0,0)
    rightLowerCorner = group2ForBox2[0][0][1]
    box2 = box2Uncropped.crop((leftUpperCorner[0]+margin,leftUpperCorner[1]+margin,rightLowerCorner[0]-margin,rightLowerCorner[1]-margin))
    # Box 4,5,6,7:
    groupForBox4 = groupForBox2
    bxesFor4 = boxing(groupForBox4,coords[3])
    box4Uncropped = im.crop(bxesFor4[0])
    t7 = t.append(time())
    verLinesFor4 = searchVerticalLines(box4Uncropped,box4Uncropped.size[1],0,10) # <-- Takes time
    t8 = t.append(time())
    group2ForBox4 = groupingH(verLinesFor4,4)
    #There must be 5 groups.

    # Error raising mechanism needed here
    maleBox = box4Uncropped.crop((group2ForBox4[1][len(group2ForBox4[1])-1][0][0]+margin,0+margin,group2ForBox4[2][0][0][0]-margin,box4Uncropped.size[1]-margin))
    femaleBox = box4Uncropped.crop((group2ForBox4[2][len(group2ForBox4[2])-1][0][0]+margin,0+margin,group2ForBox4[3][0][0][0]-margin,box4Uncropped.size[1]-margin))
    third_gender = box4Uncropped.crop((group2ForBox4[3][len(group2ForBox4[3])-1][0][0]+margin,0+margin,group2ForBox4[4][0][0][0]-margin,box4Uncropped.size[1]-margin))
    total = box4Uncropped.crop((group2ForBox4[4][len(group2ForBox4[4])-1][0][0]+margin,0+margin,box4Uncropped.size[0]-margin,box4Uncropped.size[1]-margin))

    # Box 8, 10:
    groupForBox8 = groupForBox2
    bxesFor8 = boxing(groupForBox8,coords[4])
    box8Uncropped = im.crop(bxesFor8[0])
    t9 = t.append(time())
    verLinesFor8 = searchVerticalLines(box8Uncropped,box8Uncropped.size[1],0,10) # <--Takes time
    t10 = t.append(time())
    group2ForBox8 = groupingH(verLinesFor8,4)
    box10 = box8Uncropped.crop((group2ForBox8[0][len(group2ForBox8)-1][0][0]+margin,0+margin,box8Uncropped.size[0]-margin,box8Uncropped.size[1]-margin))
    box8 = box8Uncropped.crop((0+margin,0+margin,group2ForBox8[0][0][0][0]-margin,box8Uncropped.size[1]-margin))

    # Box 9:
    groupForBox9 = groupForBox2
    bxesFor9= boxing(groupForBox9,coords[5])
    box9 = im.crop((bxesFor9[0][0]+margin,bxesFor9[0][1]+margin,bxesFor9[0][2]-margin,bxesFor9[0][3]-margin))
    for i in range(0,len(t)-1):
        print('Time taken :'+str(t[i+1]-t[i]))
    return [box1,box2,maleBox,femaleBox,third_gender,total,box8,box9,box10]
def processBoxes(bxLst):
    opList = []
    for i,box in enumerate(bxLst):
        print("box :"+str(i))
        opList.append(pt.image_to_string(box,lang='hin+eng',config='--psm 6'))
    return opList

def getFrontPageInfo(im,pg,coords):
    """
    coords[0]: List of lengths of horizontal lines to be recognized: 0th for box1, 1st for box2+3, 
        2nd for boxes 4,5,6,7, 3rd for boxes 8 and 10, 4th for box 9
    coords[1]: List of lengths of vertical lines to be recognized: 0th for box1
    coords[2]: Height of box 2,3
    coords[3]: Height of box 4,5,6,7
    coords[4]: Height of box 8,10
    coords[5]: Height of box 9
    """
    boxList = getFrontPageBoxes(im,pg,coords)
    return processBoxes(boxList)

Answer 1

查看我的带有注释的代码以获取更多详细信息。我只是做了一个只有 1 盒的 sample 。将同样的方法应用到其他人身上。

import cv2

img = cv2.imread("1.png")


imgray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
ret,thresh = cv2.threshold(imgray,127,255,0)
cv2.bitwise_not(thresh,thresh)

im2, contours, hierarchy = cv2.findContours(thresh,cv2.RETR_EXTERNAL,cv2.CHAIN_APPROX_SIMPLE)

#find the document in the image
max_area = 0
max_contour = None
ind = 0
for i,c in enumerate(contours):
    area = cv2.contourArea(c)
    if area>max_area:
        max_area = area
        max_contour = c
        ind = i
cv2.drawContours(img, contours, ind ,(0,0,255), 2)

#extract the document
rect = cv2.boundingRect(max_contour)
roi = img[rect[1]:rect[1]+rect[3],rect[0]:rect[0]+rect[2]]

(h,w) = roi.shape[:2]

#create a mask (the mask of box 1)
mask1 = (0,0,w*0.88,h*0.062) #the parameter 0.88 and 0.062 were found base on the format of the document
cv2.rectangle(roi,(mask1[0],mask1[1]),(int(mask1[2]),int(mask1[3])),(0,255,0),2)


cv2.imshow("img",img)
cv2.imshow("ROI",roi)
cv2.waitKey()
cv2.destroyAllWindows()