opencv部分基本操作:读图片，视频，画矩形，圆形，直线，写字

基本读取

读图像

import cv2 as cv
# 读一个图像，返回它的矩阵. img = cv.imread(filename="文件路径")
img = cv.imread(filename="./cat.jpg")
# 显示图像矩阵.cv.imshow(winname="窗口名", mat="图像矩阵")
cv.imshow(winname="test", mat=img)
cv.waitKey(0)

效果

读视频1，从摄像头获取视频

注：按d键退出

def readvideo():
    # 0代表调用本地摄像头
    capture = cv.VideoCapture(0)
    while True:
        isTrue, frame = capture.read()
        cv.imshow(winname="camera from pc", mat=frame)
        if cv.waitKey(20) & 0xFF==ord('d'):
            break
    capture.release()
    cv.destroyAllWindows()
readvideo()

效果

读视频2，从本地文件的视频获取

注：按d键退出

def readvideo2():
    # 指定路径即可
    capture = cv.VideoCapture('./video.mp4')
    while True:
        isTrue, frame = capture.read()
        cv.imshow(winname="video from pc", mat=frame)
        if cv.waitKey(20) & 0xFF==ord('d'):
            break
    capture.release()
    cv.destroyAllWindows()
readvideo2()

效果

读视频2，从本地文件视频获取。且缩小视频的尺寸

注：这个rescalevideo，适用于图片，视频，摄像头

import cv2 as cv
def rescalevideo(frame, size=0.5):
    width = frame.shape[1] * size
    width = int(width)
    heigh = frame.shape[0] * size
    heigh = int(heigh)
    dimensions = (width, heigh)
    return cv.resize(src=frame, dsize=dimensions,
    interpolation=cv.INTER_AREA
    )
def readvideo2():
    # 指定路径即可
    capture = cv.VideoCapture('./video.mp4')
    while True:
        isTrue, frame = capture.read()
        newframe = rescalevideo(frame)
        cv.imshow(winname="video from pc", mat=frame)
        cv.imshow(winname="low size video", mat=newframe)
        if cv.waitKey(20) & 0xFF==ord('d'):
            break
    capture.release()
    cv.destroyAllWindows()
readvideo2()

效果

画线等操作

画一个纯黑的图像

import cv2 as cv
import numpy as np

创建一个黑色的图像

blank = np.zeros(shape=(200, 200), dtype="uint8")
cv.imshow("blank", blank)
cv.waitKey(0)

效果

在黑色图像上画一个矩形

import cv2 as cv
import numpy as np
# 创建一个黑色的图像
# 这里要增加3，表示rgb三层通道
blank = np.zeros(shape=(200, 200, 3), dtype="uint8")

cv.imshow("blank0", blank)
cv.rectangle(blank, pt1=(0,0),pt2=(100,100), color=(0,255,0), thickness=3)
cv.imshow("blank1", blank)
cv.waitKey(0)

效果

填充矩形

注：和上述操作类似，给thickness设置为cv.FILLED或者-1

import cv2 as cv
import numpy as np
# 创建一个黑色的图像
# 这里要增加3，表示rgb三层通道
blank = np.zeros(shape=(200, 200, 3), dtype="uint8")

cv.imshow("blank0", blank)
cv.rectangle(blank, pt1=(0,0),pt2=(100,100), color=(0,255,0), thickness=cv.FILLED)
cv.imshow("blank1", blank)
cv.waitKey(0)

效果

画矩形加圆形

注：和上述操作类似，如果想要填充圆形，给thickness设置为cv.FILLED或者-1

import cv2 as cv
import numpy as np
# 创建一个黑色的图像
# 这里要增加3，表示rgb三层通道
blank = np.zeros(shape=(200, 200, 3), dtype="uint8")
cv.imshow("blank0", blank)
cv.rectangle(blank, pt1=(0,0),pt2=(100,100), color=(0,255,0), thickness=cv.FILLED)
cv.imshow("blank1", blank)
# 增加圆圈的显示
cv.circle(blank, center=(100,100), radius=59, color=(0,0,255), thickness=3)
cv.imshow("rectangle and circle", blank)
cv.waitKey(0)

结果

注：部分重复在上方，这里只展示关键代码

画线

# 增加直线
cv.line(blank, pt1=(0,0), pt2=(100,100), color=(255,0,0), thickness=5)
cv.imshow("line", blank)

效果

显示文字