python opencv鼠標畫點之cv2.drawMarker()函數
前言
這裡所謂畫點的意思是指在單一像素點上畫一個標記符,而不是畫小圓點。使用的函數是cv2.drawMarker(img, position, color, …)
關於鼠標回調函數的說明可以參考:opencv-python的鼠標交互操作
cv2.drawMarker()函數說明
參數說明
導入cv2後,通過help(cv2.drawMarker)可以看到函數的幫助文檔如下:
drawMarker(...) drawMarker(img, position, color[, markerType[, markerSize[, thickness[, line_type]]]]) -> img . @brief Draws a marker on a predefined position in an image. . . The function cv::drawMarker draws a marker on a given position in the image. For the moment several . marker types are supported, see #MarkerTypes for more information. . . @param img Image. . @param position The point where the crosshair is positioned. . @param color Line color. . @param markerType The specific type of marker you want to use, see #MarkerTypes . @param thickness Line thickness. . @param line_type Type of the line, See #LineTypes . @param markerSize The length of the marker axis [default = 20 pixels]
其中三個必選參數:img, position, color,其他參數是可選。三個必選參數說明如下:
- img:底圖,uint8類型的ndarray,
- position:坐標,是一個包含兩個數字的tuple(必需是tuple),表示(x, y)
- color:顏色,是一個包含三個數字的tuple或list,表示(b, g, r)
其他參數說明如下:
- markerType:點的類型。取值0-6,有相應的宏定義與之對應,具體的可參考下面的一個表。
- markerSize:點的大小。大於0的整數,必需是整數。實際輸入<=0的數字也可,但是估計程序裡有判斷,<=0等同於1。默認值是20。
- thickness:點的線寬。必需是大於0的整數,必需是整數,不能小於0,默認值是1。
- line_type:線的類型。可以取的值有cv2.LINE_4,cv2.LINE_8,cv2.LINE_AA。其中cv2.LINE_AA的AA表示抗鋸齒,線會更平滑。
markerType取值說明
數值 | 宏定義 | 說明 |
---|---|---|
0 | cv2.MARKER_CROSS | 十字線(橫豎兩根線) |
1 | cv2.MARKER_TILTED_CROSS | 交叉線(斜著兩根線) |
2 | cv2.MARKER_STAR | 米字線(橫豎加斜著共四根線) |
3 | cv2.MARKER_DIAMOND | 旋轉45度的正方形 |
4 | cv2.MARKER_SQUARE | 正方形 |
5 | cv2.MARKER_TRIANGLE_UP | 尖角向上的三角形 |
6 | cv2.MARKER_TRIANGLE_DOWN | 尖角向下的三角形 |
markerType示例
下面是一個簡單的畫點程序
# -*- coding: utf-8 -*- import cv2 import numpy as np if __name__ == '__main__': image = np.zeros((256, 256, 3), np.uint8) color = (0, 255, 0) cv2.drawMarker(image, (50, 50), color, markerType=0) cv2.drawMarker(image, (100, 50), color, markerType=1) cv2.drawMarker(image, (150, 50), color, markerType=2) cv2.drawMarker(image, (200, 50), color, markerType=3) cv2.drawMarker(image, (50, 100), color, markerType=4) cv2.drawMarker(image, (100, 100), color, markerType=5) cv2.drawMarker(image, (150, 100), color, markerType=6) cv2.namedWindow('marker_type', 1) cv2.imshow('marker_type', image) cv2.waitKey(0) cv2.destroyAllWindows()
請特別註意,opencv在調用這些畫圖函數後,image的內容會被這些畫圖函數改變,也就是說,函數調用之後,我們就拿不回原始的image瞭,除非另外保存一份原始image的副本。在寫一些交互畫圖函數時,這個特性需要格外註意。
程序執行結果如下。
利用鼠標回調函數交互式畫點
例1,簡單的例子
該例子與 中的例子相同
# -*- coding: utf-8 -*- import cv2 import numpy as np WIN_NAME = 'pick_points' def onmouse_pick_points(event, x, y, flags, param): if event == cv2.EVENT_LBUTTONDOWN: print('x = %d, y = %d' % (x, y)) cv2.drawMarker(param, (x, y), (0, 255, 0)) if __name__ == '__main__': image = np.zeros((256, 256, 3), np.uint8) cv2.namedWindow(WIN_NAME, 0) cv2.setMouseCallback(WIN_NAME, onmouse_pick_points, image) while True: cv2.imshow(WIN_NAME, image) key = cv2.waitKey(30) if key == 27: # ESC break cv2.destroyAllWindows()
上面程序中有幾個註意點:
- setMouseCallback()中的param參數我們傳遞瞭image進去,也就是說鼠標回調函數onmouse_pick_points()中的param就是image,畫點的操作在鼠標回調函數中,該參數在onmouse_pick_points中的變化可以保留到函數外,可以理解為C++的引用傳遞,或C語言的指針傳遞。
- 需要一個無限循環來刷新圖像。
- 無限循環的退出條件由鍵盤獲取,cv2.waitKey()用來獲取鍵盤的按鍵,當我們點ESC後就可以退出。
這裡點瞭三次左鍵,終端輸出以下內容:
x = 60, y = 55 x = 206, y = 113 x = 114, y = 192
並得到這樣一張圖像:
例2,刪除功能
如果需要刪除已經畫瞭的點的功能,那麼問題就變得略有些復雜瞭。
我們之前講過,opencv在畫瞭這些點之後,圖像的像素已經事實上被改變瞭,想要緊緊通過當前圖像將其恢復原狀是不行的。所以為瞭實現刪除功能,我們需要備份一張原始圖像,一張用來對外顯示的圖像,以及一個由點坐標組成的list。
每次做刪除點的操作後,我們都使用原始圖像重置對外顯示的圖像,然後再把list中所有的點都重新畫在對外顯示的圖像上,就可以實現刪除點的效果。如果是增加點的操作,則不用重置圖像。
實現代碼如下:
下面代碼中,左鍵實現增加一個點的操作,右鍵依次刪除後面畫上的點。
# -*- coding: utf-8 -*- import cv2 import numpy as np WIN_NAME = 'pick_points' class DrawPoints(object): def __init__(self, image, color, marker_type=cv2.MARKER_CROSS, marker_size=20, thickness=1): """ Initialization of class DrawPoints Parameters ---------- image: ndarray source image. shape is [height, width, channels] color: tuple a tuple containing uint8 integers, designating B, G, R values, separately marker_type: int marker type, between [0, 6] marker_size: int marker size, >=1 thickness: int line thickness, >=1 """ self.original_image = image self.image_for_show = image.copy() self.color = color self.marker_type = marker_type self.marker_size = marker_size self.thickness = thickness self.pts = [] def append(self, x, y): """ add a point to points list Parameters ---------- x, y: int, int coordinate of a point """ self.pts.append((x, y)) def pop(self): """ pop a point from points list """ pt = () if self.pts: pt = self.pts.pop() return pt def reset_image(self): """ reset image_for_show using original image """ self.image_for_show = self.original_image.copy() def draw(self): """ draw points on image_for_show """ for pt in self.pts: cv2.drawMarker(self.image_for_show, pt, color=self.color, markerType=self.marker_type, markerSize=self.marker_size, thickness=self.thickness) def onmouse_pick_points(event, x, y, flags, draw_pts): if event == cv2.EVENT_LBUTTONDOWN: print('add: x = %d, y = %d' % (x, y)) draw_pts.append(x, y) draw_pts.draw() elif event == cv2.EVENT_RBUTTONDOWN: pt = draw_pts.pop() if pt: print('delete: x = %d, y = %d' % (pt[0], pt[1])) draw_pts.reset_image() draw_pts.draw() if __name__ == '__main__': image = np.zeros((256, 256, 3), np.uint8) draw_pts = DrawPoints(image, (0, 255, 0)) cv2.namedWindow(WIN_NAME, 0) cv2.setMouseCallback(WIN_NAME, onmouse_pick_points, draw_pts) while True: cv2.imshow(WIN_NAME, draw_pts.image_for_show) key = cv2.waitKey(30) if key == 27: # ESC break cv2.destroyAllWindows()
終端輸出如下:
add: x = 54, y = 51
add: x = 215, y = 81
add: x = 123, y = 121
add: x = 57, y = 197
add: x = 168, y = 210
delete: x = 168, y = 210
delete: x = 57, y = 197
得到的結果如下:
總結
到此這篇關於python opencv鼠標畫點之cv2.drawMarker()函數的文章就介紹到這瞭,更多相關opencv鼠標畫點cv2.drawMarker()內容請搜索WalkonNet以前的文章或繼續瀏覽下面的相關文章希望大傢以後多多支持WalkonNet!
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