所谓瞄准星指的是一个圆圈加一个圆圈内的十字线,就像玩射击游戏狙击枪开镜的样子一样。这里并不是直接在图上画一个瞄准星,而是让这个瞄准星跟着鼠标走。在图像标注任务中,可以利用瞄准星进行一些辅助,特别是回归类的任务,使用该功能可以使得关键点的标注更加精准。
关于鼠标回调函数的说明可以参考:opencv-python的鼠标交互操作
函数说明
import cv2后,可以分别help(cv2.circle)和help(cv2.line)查看两个函数的帮助信息:
cv2.circle()
其中四个必选参数:
img:底图,uint8类型的ndarray
center:圆心坐标,是一个包含两个数字的tuple(必需是tuple),表示(x, y)
radius:圆半径,必需是整数
color:颜色,是一个包含三个数字的tuple或list,表示(b, g, r)
其他是可选参数:
thickness:点的线宽。必需是大于0的整数,必需是整数,不能小于0。默认值是1
lineType:线的类型。可以取的值有cv2.LINE_4,cv2.LINE_8,cv2.LINE_AA。其中cv2.LINE_AA的AA表示抗锯齿,线会更平滑,画圆的时候使用该类型比较好。
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.
其中四个必选参数:
img:底图,uint8类型的ndarray
pt1:起点坐标,是一个包含两个数字的tuple(必需是tuple),表示(x, y)
pt2:终点坐标,类型同上
color:颜色,是一个包含三个数字的tuple或list,表示(b, g, r)
其他是可选参数:
thickness:点的线宽。必需是大于0的整数,必需是整数,不能小于0。默认值是1
lineType:线的类型。可以取的值有cv2.LINE_4,cv2.LINE_8,cv2.LINE_AA。其中cv2.LINE_AA的AA表示抗锯齿,线会更平滑,画圆的时候使用该类型比较好。
简单的例子
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# -*- 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) |
结果如下:
利用鼠标回调函数画瞄准星
操作说明:
鼠标移动时以鼠标为圆心跟随一个瞄准星
鼠标滚轮控制瞄准星的大小
+, -号控制鼠标滚轮时瞄准星的变化量
代码如下:
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# -*- 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() |
结果如下,有了瞄准星的辅助,我们可以更加精准地找到Luka的眼睛中心。同理,我们在做人脸关键点标注时,这个功能也可以让我们更加精准地找到人眼睛的中心。
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原文链接:https://blog.csdn.net/bby1987/article/details/107302410