python - 如何检测图像上的符号并保存？

Question

我创建了可以识别不同数字和字符的简单神经网络。我想让神经网络识别汽车上的车牌。为此，我必须将图像上的符号分开。例如，我必须在图像上找到符号并将每个符号保存到文件(png 或 jpg):

源图片:

创立符号:

文件中的分隔符号:

如何使用 python 找到符号并将绿色矩形保存到简单的 png(或 jpg)文件？

Answer 1

如果您希望使用 OpenCV 执行，您可以查看此解决方案:

您可以通过查找特定区域上方的轮廓来执行符号检测。它们对应的边界框可以绘制在相同形状的空白图像上。

import cv2

img = cv2.imread(r'C:\Users\Desktop\pic.png') 
cv2.imshow('Image', img)

#--- create a blank image of the same size for storing the green rectangles (boundaries) ---
black = np.zeros_like(img)

#--- convert your image to grayscale and apply a threshold ---
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
ret2, th2 = cv2.threshold(gray, 0, 255, cv2.THRESH_BINARY + cv2.THRESH_OTSU)

#--- perform morphological operation to ensure smaller portions are part of a single character ---
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (5, 5))
threshed = cv2.morphologyEx(th2, cv2.MORPH_CLOSE, kernel)

#--- find contours ---
imgContours, Contours, Hierarchy = cv2.findContours(threshed, cv2.RETR_EXTERNAL, cv2.CHAIN_APPROX_NONE)
for contour in Contours:

    #--- select contours above a certain area ---
    if cv2.contourArea(contour) > 200:

        #--- store the coordinates of the bounding boxes ---
        [X, Y, W, H] = cv2.boundingRect(contour)

        #--- draw those bounding boxes in the actual image as well as the plain blank image ---
        cv2.rectangle(img2, (X, Y), (X + W, Y + H), (0,0,255), 2)
        cv2.rectangle(black, (X, Y), (X + W, Y + H), (0,255,0), 2)

cv2.imshow('contour', img2)
cv2.imshow('black', black)

结果如下: