我这里有一行代码，使用了OpenCV的Python绑定：
cv2.rectangle(img, (box[1], box[0]), (box[3], box[2]), (255,0,0), 4)
这会在图像img上绘制一条红色矩形，线条粗细为4。
但是有没有办法使矩形的线条风格更加独特？并不需要太多，只需要点线或虚线就可以了。
OpenCV矩形使用虚线或点线
16
- user961627
1
两个建议：1）使用Python子进程调用Imagemagick，它可以绘制虚线（或使用Python Wand，它使用Imagemagick）。或者2）将矩形作为黑色蒙版上的白色线条绘制，然后在蒙版上绘制一组黑色线条（水平和垂直线条），以在白色线条中放置间隙。线条厚度将控制间隙。然后使用蒙版在图像上绘制黑色，其中线条是白色的。 - fmw42
7个回答
18
import cv2
import numpy as np
def drawline(img,pt1,pt2,color,thickness=1,style='dotted',gap=20):
dist =((pt1[0]-pt2[0])**2+(pt1[1]-pt2[1])**2)**.5
pts= []
for i in np.arange(0,dist,gap):
r=i/dist
x=int((pt1[0]*(1-r)+pt2[0]*r)+.5)
y=int((pt1[1]*(1-r)+pt2[1]*r)+.5)
p = (x,y)
pts.append(p)
if style=='dotted':
for p in pts:
cv2.circle(img,p,thickness,color,-1)
else:
s=pts[0]
e=pts[0]
i=0
for p in pts:
s=e
e=p
if i%2==1:
cv2.line(img,s,e,color,thickness)
i+=1
def drawpoly(img,pts,color,thickness=1,style='dotted',):
s=pts[0]
e=pts[0]
pts.append(pts.pop(0))
for p in pts:
s=e
e=p
drawline(img,s,e,color,thickness,style)
def drawrect(img,pt1,pt2,color,thickness=1,style='dotted'):
pts = [pt1,(pt2[0],pt1[1]),pt2,(pt1[0],pt2[1])]
drawpoly(img,pts,color,thickness,style)
im = np.zeros((800,800,3),dtype='uint8')
s=(234,222)
e=(500,700)
drawrect(im,s,e,(0,255,255),1,'dotted')
cv2.imshow('im',im)
cv2.waitKey()
- Zaw Lin
1
这真难以跟进 - 给你的变量命名并正确注释代码 - MattieG4
7
- openCV is opensource library so you can find source code for drawing and modify it slightly
you can use LineIterator and get any style you want in a few lines of code
void lineDot(OutputArray img, const Point& pt1, const Point& pt2, const Scalar& color, const vector<bool>& pattern){ LineIterator it(img.getMat(), pt1, pt2, LINE_8); // LINE_AA is not supported here for(auto i=0; i<it.count; i++, it++){ if(pattern[i%pattern.size()]){ // use any pattern of any length, dotted is {0,0,1}, dashed is {0,0,0,1,1,1} etc (*it)[0] = color.val[0]; (*it)[1] = color.val[1]; (*it)[2] = color.val[2]; } } }
- Vit
7
OpenCV目前不支持线条属性，除了线条的粗细和抗锯齿。
- Adi Shavit
1
这是一种在Python/OpenCV中绘制虚线的方法。
将矩形作为白色线条在黑色背景上绘制，然后在该掩模上绘制一组黑色线条（水平和垂直线条），以在白色线条中间留出间隔。线条的粗细将控制间隔的大小。然后使用该掩模，在图像上绘制黑色线条的位置处绘制黑色。
输入：
import cv2
import numpy as np
# read the image
img = cv2.imread('lena.jpg')
# draw white lines on black as mask
mask = np.zeros_like(img)
cv2.rectangle(mask, (50,50), (200,200), (255,255,255), 4)
# draw grid of black lines on white
grid = np.full_like(img, (255,255,255))
dx, dy = 23, 23 # spacing cannot be evenly divisible with dimensions of rectangle
grid[:,::dx,:] = [0,0,0]
grid[::dy,:,:] = [0,0,0]
# thicken grid lines
kernel = cv2.getStructuringElement(cv2.MORPH_RECT, (5,5))
grid2 = cv2.morphologyEx(grid, cv2.MORPH_ERODE, kernel)
# multiply grid with mask
mask2 = cv2.multiply(mask, grid2)
mask2 = cv2.cvtColor(mask2, cv2.COLOR_BGR2GRAY)
# use mask to draw blue dashed rectangle on image
result = img.copy()
result[mask2==255] = [255,0,0]
# save results
cv2.imwrite('lena_mask.jpg', mask)
cv2.imwrite('lena_grid.jpg', grid)
cv2.imwrite('lena_grid2.jpg', grid2)
cv2.imwrite('lena_mask2.jpg', mask2)
cv2.imwrite('lena_dashed_lines.jpg', result)
# show results
cv2.imshow('mask', mask)
cv2.imshow('grid', grid)
cv2.imshow('grid2', grid2)
cv2.imshow('mask2', mask2)
cv2.imshow('result', result)
cv2.waitKey(0)
矩形遮罩：
黑色网格：
网格加粗：
结果：
- fmw42
2
这只有在矩形位于图像中间时才有效。如果不是的话，矩形的虚线可能会变得不均匀，特别是当它很小的时候。 - MattieG4
不对。只要矩形和网格对齐，就应该可以正常工作。 - fmw42
0
OpenCV目前没有内置的绘制虚线的方法，正如Adi Shavit和其他人在这里所述。
然而，有一个解决方法可以使用cv2.line()函数来绘制虚线。一种方法是绘制短线段并在它们之间留出间隔，以呈现虚线的外观。以下是一个示例代码片段，演示了这种技术：
import cv2
# Create a black image
img = np.zeros((512, 512, 3), np.uint8)
# Draw a dashed line
start_point = (100, 100)
end_point = (400, 100)
color = (0, 255, 0)
thickness = 2
# Define the length of the line segments and gaps
segment_length = 10
gap_length = 5
# Calculate the length and direction of the line
dx = end_point[0] - start_point[0]
dy = end_point[1] - start_point[1]
line_length = np.sqrt(dx*dx + dy*dy)
x_unit = dx / line_length
y_unit = dy / line_length
# Draw the line segments
current_point = start_point
while line_length >= segment_length:
end_point = (int(current_point[0] + segment_length*x_unit), int(current_point[1] + segment_length*y_unit))
cv2.line(img, current_point, end_point, color, thickness)
current_point = (int(end_point[0] + gap_length*x_unit), int(end_point[1] + gap_length*y_unit))
line_length -= segment_length + gap_length
# Display the image
cv2.imshow('Dashed Line', img)
cv2.waitKey(0)
cv2.destroyAllWindows()
在这个例子中，从点（100, 100）到点（400, 100）绘制了一条绿色虚线，线宽为2像素。segment_length和gap_length变量分别控制线段和间隙的长度。代码计算出线的长度和方向，然后迭代地绘制短线段，并在它们之间留有间隙，直到整条线被绘制完毕。可以根据需要调整此方法以产生不同的虚线模式和长度。
另一种选择是使用其他库，如PIL或Pillow，例如：
from PIL import Image, ImageDraw
# Create a black image
img = Image.new('RGB', (512, 512), (0, 0, 0))
# Draw a dashed line
draw = ImageDraw.Draw(img)
start_point = (100, 100)
end_point = (400, 100)
color = (0, 255, 0)
dash_length = 10
gap_length = 5
dash = [dash_length, gap_length]
draw.line((start_point, end_point), fill=color, width=2, joint='curve', dash=dash)
# Display the image
img.show()
- Shahar Gino
0
这是我Python课上的内容。
@staticmethod
def draw_dashed_line(image, point1: tuple[int, int], point2: tuple[int, int], color: tuple[int, int, int], thickness: int = 1,
dash_size: int = 20):
"""
This assumes the line is vertical or horizontal
:param image: image to draw the line onto
:param point1: (x, y)
:param point2: (x, y)
:param color: color of the line
:param thickness: thickness of the line
:param dash_size: length of the gap and dash
:return:
"""
x1 = point1[0]
y1 = point1[1]
x2 = point2[0]
y2 = point2[1]
if x1 == x2:
# vertical line
if y2 > y1:
max_y = y2
min_y = y1
elif y1 > y2:
max_y = y1
min_y = y2
else:
raise ValueError("Both points cannot be identical")
for y in range(min_y, max_y, dash_size):
cv2.line(image, (x1, y), (x1, y + round(dash_size/2)), color, thickness)
elif y1 == y2:
# horizontal line
if x2 > x1:
max_x = x2
min_x = x1
elif x1 > x2:
max_x = x1
min_x = x2
for x in range(min_x, max_x, dash_size):
cv2.line(image, (x, y1), (x + round(dash_size/2), y1), color, thickness)
else:
raise ValueError("Line must be horizontal or vertical")
def draw_dashed_bounding_box(self, image, centre_point: tuple[int, int], size: tuple[int, int], color: tuple[int, int, int],
thickness: int, dash_length: int = 20) -> None:
"""
Draw a rectangular bounding box
:param image: image to draw the bounding box onto
:param centre_point: centre point of the bounding box
:param size: (height, width) of the bounding box
:param color: RGB colour of the bounding box
:param thickness: thickness of lines
:param dash_length: length of gap and lines for dashes in bounding box lines
:return:
"""
min_x = int(centre_point[0] - (size[0] / 2))
min_y = int(centre_point[1] - (size[1] / 2))
max_x = int(centre_point[0] + (size[0] / 2))
max_y = int(centre_point[1] + (size[1] / 2))
points = [(min_x, min_y), (max_x, min_y), (max_x, max_y), (min_x, max_y)]
end = points[0]
points.append(points.pop(0))
for point in points:
start = end
end = point
self.draw_dashed_line(image, start, end, color, thickness, dash_length)
- MattieG4
-3
尝试像这样做：
cv::Point P1, P2;
P1.y = 50;
P2.y = 50;
int dot_gap = 50;
int dot_width = 50;
for( int i=0 ; i < in_img.cols; (i = i+d_width) ) {
P1.x = i;
P2.x = i + dot_width;
cv::line(in_img, P1, P2, cv::Scalar(0, 255, 255), 2, cv::LINE_8);
}
- Sam
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