opencv图像的输入输出

导入cv2
import cv2 
读入图片，通道顺序为BGR,与matpotlib相反
img = cv2.imread('filename.jpg')
转灰度图像
img_gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY)
命名窗口
cv2.namedWindow('demo')
显示图像
cv2.imshow('demo',img)
等待按键
cv2.waitKey(0) 　#waitKey()括号中表示等待毫秒数，0表示永远等待．
图像输出
quality = 90,[]可选
cv2.imwrite(savepath,img,[cv2.IMWRITE_JPEG_QUALITY,quality]])
字节序列与图像的相互转换
import numpy as np
从字节序列读取图像
png_str = open('img_8bit.png','rb')
png_data = np.frombuffer(png_str,np.uint8)
img = cv2.imdecode(png_data,cv2.IMREAD_UNCHANGED)
图像写到字节序列
res,jpg_data = cv2.imencode('xxx.jpg',img)
jpg_str = jpg_data.tobytes()