Python+OpenCV實現鼠標畫瞄準星的方法詳解
所謂瞄準星指的是一個圓圈加一個圓圈內的十字線,就像玩射擊遊戲狙擊槍開鏡的樣子一樣。這裡並不是直接在圖上畫一個瞄準星,而是讓這個瞄準星跟著鼠標走。在圖像標註任務中,可以利用瞄準星進行一些輔助,特別是回歸類的任務,使用該功能可以使得關鍵點的標註更加精準。
關於鼠標回調函數的說明可以參考:opencv-python的鼠標交互操作
函數說明
import cv2後,可以分別help(cv2.circle)和help(cv2.line)查看兩個函數的幫助信息:
cv2.circle()
其中四個必選參數:
img:底圖,uint8類型的ndarray
center:圓心坐標,是一個包含兩個數字的tuple(必需是tuple),表示(x, y)
radius:圓半徑,必需是整數
color:顏色,是一個包含三個數字的tuple或list,表示(b, g, r)
其他是可選參數:
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
lineType: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,畫圓的時候使用該類型比較好。
cv2.line()
line(img, pt1, pt2, color[, thickness[, lineType[, shift]]]) -> img
. @brief Draws a line segment connecting two points.
.
. The function line draws the line segment between pt1 and pt2 points in the image. The line is
. clipped by the image boundaries. For non-antialiased lines with integer coordinates, the 8-connected
. or 4-connected Bresenham algorithm is used. Thick lines are drawn with rounding endings. Antialiased
. lines are drawn using Gaussian filtering.
.
. @param img Image.
. @param pt1 First point of the line segment.
. @param pt2 Second point of the line segment.
. @param color Line color.
. @param thickness Line thickness.
. @param lineType Type of the line. See #LineTypes.
. @param shift Number of fractional bits in the point coordinates.
其中四個必選參數:
img:底圖,uint8類型的ndarray
pt1:起點坐標,是一個包含兩個數字的tuple(必需是tuple),表示(x, y)
pt2:終點坐標,類型同上
color:顏色,是一個包含三個數字的tuple或list,表示(b, g, r)
其他是可選參數:
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
lineType: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,畫圓的時候使用該類型比較好。
簡單的例子
# -*- coding: utf-8 -*- import cv2 import numpy as np def imshow(winname, image): cv2.namedWindow(winname, 1) cv2.imshow(winname, image) cv2.waitKey(0) cv2.destroyAllWindows() if __name__ == '__main__': image = np.zeros((256, 256, 3), np.uint8) center = (128, 128) radius = 50 color = (0, 255, 0) thickness = 2 pt_left = (center[0] - radius, center[1]) pt_right = (center[0] + radius, center[1]) pt_top = (center[0], center[1] - radius) pt_bottom = (center[0], center[1] + radius) cv2.circle(image, center, radius, color, thickness, lineType=cv2.LINE_AA) cv2.line(image, pt_left, pt_right, color, thickness) cv2.line(image, pt_top, pt_bottom, color, thickness) imshow('draw_crosshair', image)
結果如下:
利用鼠標回調函數畫瞄準星
操作說明:
鼠標移動時以鼠標為圓心跟隨一個瞄準星
鼠標滾輪控制瞄準星的大小
+, -號控制鼠標滾輪時瞄準星的變化量
代碼如下:
# -*- coding: utf-8 -*- import cv2 WIN_NAME = 'draw_crosshair' class DrawCrosshair(object): def __init__(self, image, color, center, radius, thickness=1): self.original_image = image self.image_for_show = image.copy() self.color = color self.center = center self.radius = radius self.thichness = thickness self.increment = 5 def increase_radius(self): self.radius += self.increment def decrease_radius(self): self.radius -= self.increment self.radius = max(self.radius, 0) def increase_increment(self): self.increment += 1 def decrease_increment(self): self.increment -= 1 self.increment = max(self.increment, 1) def reset_image(self): """ reset image_for_show using original image """ self.image_for_show = self.original_image.copy() def draw_circle(self): cv2.circle(self.image_for_show, center=self.center, radius=self.radius, color=self.color, thickness=self.thichness, lineType=cv2.LINE_AA) def draw_crossline(self): pt_left = (self.center[0] - self.radius, self.center[1]) pt_right = (self.center[0] + self.radius, self.center[1]) pt_top = (self.center[0], self.center[1] - self.radius) pt_bottom = (self.center[0], self.center[1] + self.radius) cv2.line(self.image_for_show, pt_left, pt_right, self.color, self.thichness) cv2.line(self.image_for_show, pt_top, pt_bottom, self.color, self.thichness) def draw(self): self.reset_image() self.draw_circle() self.draw_crossline() def onmouse_draw_rect(event, x, y, flags, draw_crosshair): if event == cv2.EVENT_MOUSEWHEEL and flags > 0: draw_crosshair.increase_radius() if event == cv2.EVENT_MOUSEWHEEL and flags < 0: draw_crosshair.decrease_radius() draw_crosshair.center = (x, y) draw_crosshair.draw() if __name__ == '__main__': # image = np.zeros((512, 512, 3), np.uint8) image = cv2.imread('luka.jpg') draw_crosshair = DrawCrosshair(image, color=(0, 255, 0), center=(256, 256), radius=100, thickness=2) cv2.namedWindow(WIN_NAME, 1) cv2.setMouseCallback(WIN_NAME, onmouse_draw_rect, draw_crosshair) while True: cv2.imshow(WIN_NAME, draw_crosshair.image_for_show) key = cv2.waitKey(30) if key == 27: # ESC break elif key == ord('+'): draw_crosshair.increase_increment() elif key == ord('-'): draw_crosshair.decrease_increment() cv2.destroyAllWindows()
結果如下,有瞭瞄準星的輔助,我們可以更加精準地找到Luka的眼睛中心。同理,我們在做人臉關鍵點標註時,這個功能也可以讓我們更加精準地找到人眼睛的中心。
到此這篇關於Python+OpenCV實現鼠標畫瞄準星的方法詳解的文章就介紹到這瞭,更多相關Python OpenCV瞄準星內容請搜索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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