python opencv鼠標畫矩形框之cv2.rectangle()函數
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.rectangle()函數說明
參數說明
導入cv2後,通過help(cv2.rectangle)可以看到函數的幫助文檔如下:
rectangle(...) rectangle(img, pt1, pt2, color[, thickness[, lineType[, shift]]]) -> img . @brief Draws a simple, thick, or filled up-right rectangle. . . The function cv::rectangle draws a rectangle outline or a filled rectangle whose two opposite corners . are pt1 and pt2. . . @param img Image. . @param pt1 Vertex of the rectangle. . @param pt2 Vertex of the rectangle opposite to pt1 . . @param color Rectangle color or brightness (grayscale image). . @param thickness Thickness of lines that make up the rectangle. Negative values, like #FILLED, . mean that the function has to draw a filled rectangle. . @param lineType Type of the line. See #LineTypes . @param shift Number of fractional bits in the point coordinates. rectangle(img, rec, color[, thickness[, lineType[, shift]]]) -> img . @overload . . use `rec` parameter as alternative specification of the drawn rectangle: `r.tl() and . r.br()-Point(1,1)` are opposite corners
其中四個參數必選:
- img:底圖,uint8類型的ndarray
- pt1:矩形框的一個頂點坐標,是一個包含兩個數字的tuple(必需是tuple),表示(x, y)
- pt2:pt1的對角線頂點坐標,類型同pt1
- color:顏色,是一個包含三個數字的tuple或list,表示(b, g, r);如果圖片是灰度圖的話,color也可以是一個數字
其他參數說明如下:
- thickness:線寬,默認值是1,數值越大表示線寬越寬;如果取值為負數或者cv2.FILLED,那麼將畫一個填充瞭的矩形
- lineType: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。
註意:pt1和pt2表示任意一對對角線上的點,不一定要求pt1必需左上角,pt2必需右下角。另外pt1和pt2可以互換順序而不影響結果。
下面是一個非交互式的程序示例
# -*- 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.rectangle(image, (20, 20), (60, 60), (0, 255, 0)) cv2.rectangle(image, (120, 120), (80, 80), (255, 0, 0), thickness=-1) cv2.rectangle(image, (140, 200), (200, 140), (0, 0, 255), thickness=5) cv2.namedWindow('rect', 1) cv2.imshow('rect', image) cv2.waitKey(0) cv2.destroyAllWindows()
第一個矩形框pt1 = 左上角,pt2 = 右下角
第二個矩形框pt1 = 右下角,pt2 = 左上角
第三個矩形框pt1 = 右上角,pt2 = 左下角
得到的結果如下:
利用鼠標回調函數交互式畫矩形框
為瞭容易理解下面程序,建議先參考下面文章的例2
opencv-python鼠標畫點:cv2.drawMarker()
下面程序的操作方法是:
- 鼠標左鍵按下開始畫當前矩形框
- 移動鼠標進行繪畫
- 彈起左鍵當前矩形框繪畫結束,並把當前矩形框加入列表
- 鼠標右鍵按下是刪除矩形框列表中的最後一個對象
編程註意事項:
- 矩形框繪畫過程中需要記錄一個鼠標左鍵按下的狀態標志。常規狀態下該標志設為False,鼠標移動不進行繪畫;當鼠標左鍵按下後,標志設為True,此時移動鼠標將進入繪畫狀態;左鍵彈起後,標志恢復False。
- 為瞭在鼠標移動過程中實時顯示繪畫狀態,需要不停地重置用來顯示的圖像,並不停地重畫所有已保存的矩形框
- 矩形框的第二個點使用shrink_point獲取,確保不超出圖像邊界
# -*- coding: utf-8 -*- import copy import cv2 import numpy as np WIN_NAME = 'draw_rect' class Rect(object): def __init__(self): self.tl = (0, 0) self.br = (0, 0) def regularize(self): """ make sure tl = TopLeft point, br = BottomRight point """ pt1 = (min(self.tl[0], self.br[0]), min(self.tl[1], self.br[1])) pt2 = (max(self.tl[0], self.br[0]), max(self.tl[1], self.br[1])) self.tl = pt1 self.br = pt2 class DrawRects(object): def __init__(self, image, color, thickness=1): self.original_image = image self.image_for_show = image.copy() self.color = color self.thickness = thickness self.rects = [] self.current_rect = Rect() self.left_button_down = False @staticmethod def __clip(value, low, high): """ clip value between low and high Parameters ---------- value: a number value to be clipped low: a number low limit high: a number high limit Returns ------- output: a number clipped value """ output = max(value, low) output = min(output, high) return output def shrink_point(self, x, y): """ shrink point (x, y) to inside image_for_show Parameters ---------- x, y: int, int coordinate of a point Returns ------- x_shrink, y_shrink: int, int shrinked coordinate """ height, width = self.image_for_show.shape[0:2] x_shrink = self.__clip(x, 0, width) y_shrink = self.__clip(y, 0, height) return (x_shrink, y_shrink) def append(self): """ add a rect to rects list """ self.rects.append(copy.deepcopy(self.current_rect)) def pop(self): """ pop a rect from rects list """ rect = Rect() if self.rects: rect = self.rects.pop() return rect def reset_image(self): """ reset image_for_show using original image """ self.image_for_show = self.original_image.copy() def draw(self): """ draw rects on image_for_show """ for rect in self.rects: cv2.rectangle(self.image_for_show, rect.tl, rect.br, color=self.color, thickness=self.thickness) def draw_current_rect(self): """ draw current rect on image_for_show """ cv2.rectangle(self.image_for_show, self.current_rect.tl, self.current_rect.br, color=self.color, thickness=self.thickness) def onmouse_draw_rect(event, x, y, flags, draw_rects): if event == cv2.EVENT_LBUTTONDOWN: # pick first point of rect print('pt1: x = %d, y = %d' % (x, y)) draw_rects.left_button_down = True draw_rects.current_rect.tl = (x, y) if draw_rects.left_button_down and event == cv2.EVENT_MOUSEMOVE: # pick second point of rect and draw current rect draw_rects.current_rect.br = draw_rects.shrink_point(x, y) draw_rects.reset_image() draw_rects.draw() draw_rects.draw_current_rect() if event == cv2.EVENT_LBUTTONUP: # finish drawing current rect and append it to rects list draw_rects.left_button_down = False draw_rects.current_rect.br = draw_rects.shrink_point(x, y) print('pt2: x = %d, y = %d' % (draw_rects.current_rect.br[0], draw_rects.current_rect.br[1])) draw_rects.current_rect.regularize() draw_rects.append() if (not draw_rects.left_button_down) and event == cv2.EVENT_RBUTTONDOWN: # pop the last rect in rects list draw_rects.pop() draw_rects.reset_image() draw_rects.draw() if __name__ == '__main__': image = np.zeros((256, 256, 3), np.uint8) draw_rects = DrawRects(image, (0, 255, 0), 2) cv2.namedWindow(WIN_NAME, 0) cv2.setMouseCallback(WIN_NAME, onmouse_draw_rect, draw_rects) while True: cv2.imshow(WIN_NAME, draw_rects.image_for_show) key = cv2.waitKey(30) if key == 27: # ESC break cv2.destroyAllWindows()
終端輸出:
pt1: x = 55, y = 68
pt2: x = 0, y = 0
pt1: x = 195, y = 60
pt2: x = 256, y = 0
pt1: x = 59, y = 192
pt2: x = 0, y = 256
pt1: x = 194, y = 190
pt2: x = 256, y = 256
pt1: x = 94, y = 111
pt2: x = 170, y = 168
結果如下:
總結
到此這篇關於python opencv鼠標畫矩形框之cv2.rectangle()函數的文章就介紹到這瞭,更多相關opencv鼠標畫矩形框cv2.rectangle()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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