Python 使用opencv查找手绘直线的端点
我试图找到一条手绘线的两个端点 我写了这个片段,找到了轮廓, 但终点并不正确:Python 使用opencv查找手绘直线的端点,python,opencv,image-processing,Python,Opencv,Image Processing,我试图找到一条手绘线的两个端点 我写了这个片段,找到了轮廓, 但终点并不正确: img = cv2.imread("my_img.jpeg") img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) # Binary Threshold: _, thr_img = cv2.threshold(img_gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU) cv2.imshow
img = cv2.imread("my_img.jpeg")
img_gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
# Binary Threshold:
_, thr_img = cv2.threshold(img_gray, 0, 255, cv2.THRESH_BINARY_INV + cv2.THRESH_OTSU)
cv2.imshow(winname="after threshold", mat=thr_img)
cv2.waitKey(0)
contours, _ = cv2.findContours(image=thr_img, mode=cv2.RETR_TREE, method=cv2.CHAIN_APPROX_SIMPLE)
for idx, cnt in enumerate(contours):
print("Contour #", idx)
cv2.drawContours(image=img, contours=[cnt], contourIdx=0, color=(255, 0, 0), thickness=3)
cv2.circle(img, tuple(cnt[0][0]), 5, (255, 255, 0), 5) # Result in wrong result
cv2.circle(img, tuple(cnt[-1][0]), 5, (0, 0, 255), 5) # Result in wrong result
cv2.imshow(winname="contour" + str(idx), mat=img)
cv2.waitKey(0)
原始图像:
我也试过cornerHarris
,但它给了我一些额外的分数
有人能推荐一种准确且更好的方法吗?此解决方案使用的是的Python实现。其思想是使用一个特殊的内核来卷积图像,该内核标识一行中的起点/终点。以下是步骤:
# imports:
import cv2
import numpy as np
# image path
path = "D://opencvImages//"
fileName = "hJVBX.jpg"
# Reading an image in default mode:
inputImage = cv2.imread(path + fileName)
# Resize image:
scalePercent = 50 # percent of original size
width = int(inputImage.shape[1] * scalePercent / 100)
height = int(inputImage.shape[0] * scalePercent / 100)
# New dimensions:
dim = (width, height)
# resize image
resizedImage = cv2.resize(inputImage, dim, interpolation=cv2.INTER_AREA)
# Color conversion
grayscaleImage = cv2.cvtColor(resizedImage, cv2.COLOR_BGR2GRAY)
grayscaleImage = 255 - grayscaleImage
到目前为止,我已经调整了图像的大小(原始比例为0.5
),并将其转换为灰度(实际上是一幅倒置的二值图像)。现在,检测端点的第一步是将线条宽度
标准化为1像素
。这是通过计算骨架来实现的,骨架可以使用OpenCV的扩展图像处理模块来实现:
这是骨架:
现在,让我们运行端点检测部分:
# Threshold the image so that white pixels get a value of 0 and
# black pixels a value of 10:
_, binaryImage = cv2.threshold(skeleton, 128, 10, cv2.THRESH_BINARY)
# Set the end-points kernel:
h = np.array([[1, 1, 1],
[1, 10, 1],
[1, 1, 1]])
# Convolve the image with the kernel:
imgFiltered = cv2.filter2D(binaryImage, -1, h)
# Extract only the end-points pixels, those with
# an intensity value of 110:
endPointsMask = np.where(imgFiltered == 110, 255, 0)
# The above operation converted the image to 32-bit float,
# convert back to 8-bit uint
endPointsMask = endPointsMask.astype(np.uint8)
查看原始链接以了解有关此方法的信息,但一般的要点是,内核是这样的:作为邻域求和的结果,与一行中的端点进行卷积将产生110
。涉及到float
操作,因此必须小心数据类型和转换。可在此处观察该程序的结果:
但是,请注意,这些是端点,如果它们太近,则可以连接一些点。现在是重复消除步骤。让我们首先定义检查点是否重复的标准。如果点太近,我们将加入他们。让我们提出一种基于形态学的点接近方法。我将用一个大小为3
和3
迭代的矩形内核扩展端点掩码。如果两个或多个点太近,它们的膨胀将产生一个大的、独特的斑点:
# RGB copy of this:
rgbMask = endPointsMask.copy()
rgbMask = cv2.cvtColor(rgbMask, cv2.COLOR_GRAY2BGR)
# Create a copy of the mask for points processing:
groupsMask = endPointsMask.copy()
# Set kernel (structuring element) size:
kernelSize = 3
# Set operation iterations:
opIterations = 3
# Get the structuring element:
maxKernel = cv2.getStructuringElement(cv2.MORPH_RECT, (kernelSize, kernelSize))
# Perform dilate:
groupsMask = cv2.morphologyEx(groupsMask, cv2.MORPH_DILATE, maxKernel, None, None, opIterations, cv2.BORDER_REFLECT101)
这是扩张的结果。我将此图像称为groupsMask
:
请注意,有些点现在是如何共享邻接的。我将使用此遮罩作为生成最终质心的指南。算法如下:循环通过端点任务
,为每个点生成一个标签。使用字典
,存储标签和共享该标签的所有质心-使用组任务
通过整体填充
在不同点之间传播标签。在字典
中,我们将存储质心簇标签、质心总和的累积以及累积的质心数量的计数,以便我们可以生成最终平均值。像这样:
# Set the centroids Dictionary:
centroidsDictionary = {}
# Get centroids on the end points mask:
totalComponents, output, stats, centroids = cv2.connectedComponentsWithStats(endPointsMask, connectivity=8)
# Count the blob labels with this:
labelCounter = 1
# Loop through the centroids, skipping the background (0):
for c in range(1, len(centroids), 1):
# Get the current centroids:
cx = int(centroids[c][0])
cy = int(centroids[c][1])
# Get the pixel value on the groups mask:
pixelValue = groupsMask[cy, cx]
# If new value (255) there's no entry in the dictionary
# Process a new key and value:
if pixelValue == 255:
# New key and values-> Centroid and Point Count:
centroidsDictionary[labelCounter] = (cx, cy, 1)
# Flood fill at centroid:
cv2.floodFill(groupsMask, mask=None, seedPoint=(cx, cy), newVal=labelCounter)
labelCounter += 1
# Else, the label already exists and we must accumulate the
# centroid and its count:
else:
# Get Value:
(accumCx, accumCy, blobCount) = centroidsDictionary[pixelValue]
# Accumulate value:
accumCx = accumCx + cx
accumCy = accumCy + cy
blobCount += 1
# Update dictionary entry:
centroidsDictionary[pixelValue] = (accumCx, accumCy, blobCount)
这里有一些程序的动画,首先,一个接一个地处理质心。我们正试图将这些似乎彼此接近的点连接起来:
正在使用新标签填充的组掩码。将共享标签的点添加在一起以生成最终平均点。这有点难看,因为我的标签从1
开始,但您几乎看不到正在填充的标签:
现在,剩下的就是得出最后的结论。循环浏览字典,检查质心及其计数。如果计数大于1
,则质心表示累加,必须除以其计数以生成终点:
# Loop trough the dictionary and get the final centroid values:
for k in centroidsDictionary:
# Get the value of the current key:
(cx, cy, count) = centroidsDictionary[k]
# Process combined points:
if count != 1:
cx = int(cx/count)
cy = int(cy/count)
# Draw circle at the centroid
cv2.circle(resizedImage, (cx, cy), 5, (0, 0, 255), -1)
cv2.imshow("Final Centroids", resizedImage)
cv2.waitKey(0)
这是最终图像,显示线条的端点/起点:
现在,端点检测方法,或者更确切地说,卷积步骤,在曲线上产生了一个明显的额外点,这可能是因为直线上的一段与其邻域过于分离——将曲线分成两部分。也许在卷积之前应用一点形态学可以解决这个问题。我想建议一种更简单、更有效的方法,更重要的是,它不会产生假端点:
想法很简单,细化后,计算相邻像素数(8连接性)如果相邻像素数等于1-->则该点为终点
代码是不言自明的:
def get_end_pnts(pnts, img):
extremes = []
for p in pnts:
x = p[0]
y = p[1]
n = 0
n += img[y - 1,x]
n += img[y - 1,x - 1]
n += img[y - 1,x + 1]
n += img[y,x - 1]
n += img[y,x + 1]
n += img[y + 1,x]
n += img[y + 1,x - 1]
n += img[y + 1,x + 1]
n /= 255
if n == 1:
extremes.append(p)
return extremes
主要内容:
输出:
编辑:您可能有兴趣访问我的答案。它有一些额外的功能,它检测端点和连接器点以及
def get_end_pnts(pnts, img):
extremes = []
for p in pnts:
x = p[0]
y = p[1]
n = 0
n += img[y - 1,x]
n += img[y - 1,x - 1]
n += img[y - 1,x + 1]
n += img[y,x - 1]
n += img[y,x + 1]
n += img[y + 1,x]
n += img[y + 1,x - 1]
n += img[y + 1,x + 1]
n /= 255
if n == 1:
extremes.append(p)
return extremes
img = cv2.imread(p, cv2.IMREAD_GRAYSCALE)
img = cv2.threshold(img, 128, 255, cv2.THRESH_OTSU + cv2.THRESH_BINARY_INV)
img = cv2.ximgproc.thinning(img)
pnts = cv2.findNonZero(img)
pnts = np.squeeze(pnts)
ext = get_end_pnts(pnts, img)
for p in ext:
cv2.circle(img, (p[0], p[1]), 5, 128)