[200 opencv routines] 217 Mouse interaction to obtain polygon area (ROI)

OpenCV routine 200 piece General catalogue

【youcans Of OpenCV routine 200 piece 】217. Mouse interaction to obtain polygon area

function cv.selectROI You can select the rectangular area of interest on the image with the mouse （ROI,region of interest）.
If you want to select the polygon area of interest on the image with the mouse , You can use mouse interaction to draw .

The function prototype ：

function cv.polylines() Used to draw polygonal curves or polylines .
function cv.fillPoly() Used to draw one or more filled polygon areas .

cv.polylines(img, pts, isClosed, color[, thickness=1, lineType=LINE_8, shift=0]) → img
cv.fillPoly(img, pts, color[, lineType=LINE_8, shift=0, offset=Point()]) → img

Parameter description ：

• img： Input / output image , Allows single channel grayscale images or multi-channel color images
• pts： Polygon vertex coordinates , A two-dimensional Numpy List of arrays
• isClosed： Closing sign ,True Represents a closed polygon ,False Indicates that the polygon is not closed

Pay special attention to polygon vertex coordinates pts The format of ：

• pts It's a list , The elements in the list are two-dimensional Numpy Array , Each element represents a set of vertex coordinates .
• A two-dimensional Numpy The shape of the array is (m,2), Each row represents the coordinates of a vertex of the polygon (xi,yi), The data format should be integer .

for example ：

    points1 = np.array([[200,100], [295,169], [259,281], [141,281], [105,169]], np.int)
    points2 = np.array([[200,400], [259,581], [105,469], [295,469], [141,581]])

points1、points2 It's in the shape of (m,2) Two dimensions of Numpy Array .
For the function cv.polylines And cv.fillPoly, You can't directly put two dimensions Numpy Array points1 or points2 As a function parameter , Instead, use it as an element of the list , Such as ： [points1]、[points2] or [points1, points2].

routine A4.9： Mouse interaction to obtain polygon area （ROI）

function cv.selectROI You can select the rectangular area of interest on the image with the mouse （ROI,region of interest）.

If you want to select the polygon area of interest on the image with the mouse , You can use mouse interaction to draw .

    # A4.9  Mouse interaction to obtain polygon area 
    def mouseHandler(event, x, y, flags, param):  #  Mouse interaction  ( Left click to select points and right click to complete )
        global drawing
        setpoint = (x, y)
        if event == cv.EVENT_LBUTTONDOWN:  #  Left mouse click events 
            drawing = True  #  Turn on drawing status 
            pts.append(setpoint)  #  Select polygon vertices 
            print(" Choose the vertex  {}：{}".format(len(pts), setpoint))
        elif event == cv.EVENT_RBUTTONDOWN:  #  Right click the event 
            drawing = False  #  End drawing state 
            print(" Finish drawing .\n ROI  Vertex coordinates ：")
            print(pts)

    #  Draw polygons interactively with the mouse  ROI
    img = cv.imread("../images/imgLena.tif")  #  Read color images (BGR)

    #  Mouse interaction  ROI
    print(" Click the left mouse button ： choice  ROI  The vertices ")
    print(" Right click ： end  ROI  choice ")
    print(" Press  ESC  sign out ")
    pts = []  # ROI  Vertex coordinate vector 
    drawing = True  #  Turn on drawing status 
    cv.namedWindow('origin')  #  Create an image window 
    cv.setMouseCallback('origin', mouseHandler)  #  The window is bound to the callback function 
    while True:
        imgCopy = img.copy()
        if len(pts) > 0:
            cv.circle(imgCopy, pts[-1], 5, (0,0,255), -1)  #  Draw the nearest vertex 
            if len(pts) > 1:
                for i in range(len(pts)-1):
                    cv.circle(imgCopy, pts[i], 5, (0,0,255), -1)  #  Draw the vertices 
                    cv.line(imgCopy, pts[i], pts[i+1], (255,0,0), 2)  #  Draw boundary segments 
            if drawing==False:
                cv.line(imgCopy, pts[0], pts[-1], (255,0,0), 2)  #  Finish the last segment 
        cv.imshow('origin', imgCopy)
        key = 0xFF & cv.waitKey(1)  #  Press  ESC  sign out 
        if key == 27:  # Esc  sign out 
            break
    cv.destroyAllWindows()  #  Image window 

    points = np.array(pts, np.int)  # ROI  Polygon vertex coordinate set 
    cv.polylines(img, [points], True, (255,255,255), 2)  #  stay  img  draw  ROI  polygon 
    mask = np.zeros(img.shape[:2], np.uint8)  #  Black Mask , single channel 
    cv.fillPoly(mask, [points], (255,255,255))  #  polygon  ROI  White window 
    imgROI = cv.bitwise_and(img, img, mask=mask)  #  Bitwise AND , from  img  Extract from  ROI

    plt.figure(figsize=(9, 6))
    plt.subplot(131), plt.title("origin image"), plt.axis('off')
    plt.imshow(cv.cvtColor(img, cv.COLOR_BGR2RGB))
    plt.subplot(132), plt.title("ROI mask"), plt.axis('off')
    plt.imshow(mask, cmap='gray')
    plt.subplot(133), plt.title("ROI cropped"), plt.axis('off')
    plt.imshow(cv.cvtColor(imgROI, cv.COLOR_BGR2RGB))
    plt.tight_layout()
    plt.show()

【 At the end of this section 】

Copyright notice ：
[email protected] Original works , Reprint must be marked with the original link ：(https://blog.csdn.net/youcans/article/details/125490992)
Copyright 2022 youcans, XUPT
Crated：2022-6-26
Welcome to your attention 『youcans Of OpenCV routine 200 piece 』 series , Ongoing update
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210. There are so many holes in drawing a straight line ？
211. Draw vertical rectangle
215. Draw approximate ellipses based on polylines
216. Draw polylines and polygons
217. Mouse interaction to obtain polygon area