如何使矩形透明？

Question

所以我正在使用 opencv，我想制作一種選擇工具，但問題是無法使矩形透明。 這是代碼：

import numpy as np
import cv2 as cv
drawing = False

def draw_rec(event,x,y,flags,param):
    global ix,iy,drawing
    if event == cv.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y
    elif event == cv.EVENT_LBUTTONUP:
        drawing = False
        cv.rectangle(img,(ix,iy),(x,y),(0,0,0),-1)
    elif event == cv.EVENT_MOUSEMOVE:
        if drawing == True:
            cv.rectangle(img, (ix, iy), (x, y), (0, 255, 0), 5)
img = cv.imread('baboon.jpg', -1)
cv.namedWindow('image')
cv.setMouseCallback('image',draw_rec)
while(1):
    cv.imshow('image',img)
    k = cv.waitKey(1) & 0xFF
    if k == 27:
        break
cv.destroyAllWindows()

Answer 1

代碼中的第一個錯誤是：

elif event == cv.EVENT_LBUTTONUP:
        drawing = False
        cv.rectangle(img,(ix,iy),(x,y),(0,0,0),-1)

-1參數表示填充矩形。 源如果我們將 -1 更改為 1：

在我看來，結果並不令人滿意。 多矩形顯示是由mouse_movement引起的。

elif event == cv.EVENT_MOUSEMOVE:
        if drawing == True:
            cv.rectangle(img, (ix, iy), (x, y), (0, 255, 0), 5)

每次鼠標移動時，都會繪制矩形。 我認為最好在鼠標移動完成時進行繪制：

代碼：

---

import numpy as np
import cv2 as cv
drawing = False

def draw_rec(event,x,y,flags,param):
    global ix,iy,drawing
    if event == cv.EVENT_LBUTTONDOWN:
        drawing = True
        ix,iy = x,y
    elif event == cv.EVENT_LBUTTONUP:
        drawing = False
        cv.rectangle(img,(ix,iy),(x,y),(0,255,0),5)


img = cv.imread('27BR1.jpg', -1)
cv.namedWindow('image')
cv.setMouseCallback('image',draw_rec)
while(1):
    cv.imshow('image',img)
    k = cv.waitKey(1) & 0xFF
    if k == 27:
        break
cv.destroyAllWindows()