如何在Python中使用OpenCV来绘制矩形框,以便在图像中标记出一些区域,用于目标检测的目的?
import cv2
cv2.rectangle(img, (x1, y1), (x2, y2), color=(255,0,0), thickness=2)
x1,y1 ------
| |
| |
| |
--------x2,y2
cv2.imwrite("my.png",img)
cv2.imshow("lalala", img)
k = cv2.waitKey(0) # 0==wait forever
正如其他答案所说,你需要使用的函数是cv2.rectangle()
,但请记住,如果将边界框定点放在元组中,则它们的坐标需要为整数,并且它们必须按照(left, top)
和(right, bottom)
或等价的(xmin, ymin)
和(xmax, ymax)
的顺序。
您可以使用cv2.rectangle()
:
cv2.rectangle(img, pt1, pt2, color, thickness, lineType, shift)
Draws a simple, thick, or filled up-right rectangle.
The function rectangle draws a rectangle outline or a filled rectangle
whose two opposite corners are pt1 and pt2.
Parameters
img Image.
pt1 Vertex of the rectangle.
pt2 Vertex of the rectangle opposite to pt1 .
color Rectangle color or brightness (grayscale image).
thickness Thickness of lines that make up the rectangle. Negative values,
like CV_FILLED , mean that the function has to draw a filled rectangle.
lineType Type of the line. See the line description.
shift Number of fractional bits in the point coordinates.
我有一个PIL图像对象,想在这个图像上绘制矩形。我想使用opencv2来绘制矩形,然后将其转换回PIL图像对象。这是我的做法:
# im is a PIL Image object
im_arr = np.asarray(im)
# convert rgb array to opencv's bgr format
im_arr_bgr = cv2.cvtColor(im_arr, cv2.COLOR_RGB2BGR)
# pts1 and pts2 are the upper left and bottom right coordinates of the rectangle
cv2.rectangle(im_arr_bgr, pts1, pts2,
color=(0, 255, 0), thickness=3)
im_arr = cv2.cvtColor(im_arr_bgr, cv2.COLOR_BGR2RGB)
# convert back to Image object
im = Image.fromarray(im_arr)
cv2.rectangle(image, pt1, pt2, color, thickness)
这里的pt1
是起点 --> (x,y),而pt2
是终点 --> (x+w,y+h)。