opencv计算机视觉学习笔记一

转载来自https://blog.csdn.net/retacn_yue/article/details/53608358
第二章 处理文件 摄像头和图形用户界面

1 基本i/o脚本

读写图像文件

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 12:22

@Author : Retacn

@Site : 读/写图像文件

@File : imageReadWrite.py

@Software: PyCharm

import cv2
import numpy as np
from matplotlib import pyplot as plt

色正方形图像

img=np.zeros((3,3),dtype=np.uint8)
print(img)

输出内容如下:

[[0 0 0]

[0 0 0]

[0 0 0]]

查看图像结构

print(img.shape)

输出结果

(3, 3)

将图像转化成BGR

img2=cv2.cvtColor(img,cv2.COLOR_BAYER_BG2BGR)
print(img2)

输出内容如下:

[[[0 0 0]

[0 0 0]

[0 0 0]]

#

[[0 0 0]

[0 0 0]

[0 0 0]]

#

[[0 0 0]

[0 0 0]

[0 0 0]]]

查看图像结构

print(img2.shape)

输出结果为:

(3, 3, 3)

将png格式图像转换为jpeg格式

image=cv2.imread(‘../j.png’)
cv2.imwrite(‘../j.jpg’,image)

imread参数

IMREAD_ANYCOLOR = 4

IMREAD_ANYDEPTH = 2

IMREAD_COLOR = 1

IMREAD_GRAYSCALE = 0 灰度图像

IMREAD_LOAD_GDAL = 8

IMREAD_UNCHANGED = -1

显示图像

plt.subplot(221),plt.imshow(img)
plt.title(“img”),plt.xticks([]),plt.yticks([])

plt.subplot(222),plt.imshow(img2)
plt.title(“img2”),plt.xticks([]),plt.yticks([])

plt.subplot(223),plt.imshow(image)
plt.title(“image”),plt.xticks([]),plt.yticks([])

plt.show()

图像与原始字节之间的转换

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 12:48

@Author : Retacn

@Site : 图像与原始字节之间的转换

@File : image2array.py

@Software: PyCharm

import cv2
import numpy as np
import os
from matplotlib import pyplot as plt

读入图像

img=cv2.imread(‘../test.jpg’,cv2.IMREAD_GRAYSCALE)
print(img)

显示转换为标准一维python bytearray

byteArray=bytearray(img)

img=cv2.imread(‘../test1.jpg’)
byteArray1=bytearray(img)

将字节转换为图像

grayImage=np.array(byteArray).reshape(220,265)
bgrImage=np.array(byteArray1).reshape(800,480,3)

将随机字节转换为灰度图像和BGR图像

创建随机字节

randomByteArray=bytearray(os.urandom(120000))
flatNumpyArray=np.array(randomByteArray)

将字节转换为400*300 的灰度图像

ran_grayImage=flatNumpyArray.reshape(300,400)

将字节转换为400*100的BGR图像

ran_bgrImage=flatNumpyArray.reshape(100,400,3)

显示图像

plt.subplot(221),plt.imshow(grayImage)
plt.title(“grayImage”),plt.xticks([]),plt.yticks([])

plt.subplot(222),plt.imshow(bgrImage)
plt.title(“bgrImage”),plt.xticks([]),plt.yticks([])

plt.subplot(223),plt.imshow(ran_grayImage)
plt.title(“ran_grayImage”),plt.xticks([]),plt.yticks([])

plt.subplot(224),plt.imshow(ran_bgrImage)
plt.title(“ran_bgrImage”),plt.xticks([]),plt.yticks([])

plt.show()

Array访问图形数据

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 13:17

@Author : Retacn

@Site : array访问图像数据

@File : arrayAccessImage.py

@Software: PyCharm

import cv2
import numpy as np
from matplotlib import pyplot as plt

读入图像

img = cv2.imread(‘../test.jpg’)
print(img[0, 0])

修改图像数据

img[0, 0] = [255, 251, 251]
print(img[0, 0])

修改指定坐标的颜色值

print(img.item(150, 120, 0))

img.itemset((150,120,0),255)
print(img.item(150, 120, 0))

图像完全没有绿色

img[:,:,1]=0

将图像的一部份复制到图像的另一个位置

img_j = cv2.imread(‘../test1.jpg’)
my_roi=img_j[0:100,0:100]
img_j[200:300,200:300]=my_roi

取得图像属性

print(img.shape)#宽度/高度/通道数
print(img.size)#图像像素的大小
print(img.dtype)#图像的数据类型

显示图像

plt.subplot(121), plt.imshow(img)
plt.title(‘change’), plt.xticks([]), plt.yticks([])

plt.subplot(122), plt.imshow(img_j)
plt.title(‘img_j’), plt.xticks([]), plt.yticks([])

plt.show()

视频文件的读写

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 13:57

@Author : Retacn

@Site : 视频文件的读写

@File : videoRead.py

@Software: PyCharm

import cv2

cameraCapture = cv2.VideoCapture(‘../test.avi’)
FPS = 30
size = (int(cameraCapture.get(cv2.CAP_PROP_FRAME_WIDTH))
, int(cameraCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
videoWrite = cv2.VideoWriter(‘../testOut.avi’, cv2.VideoWriter_fourcc(‘I’, ‘4’, ‘2’, ‘0’), FPS, size)

success, frame = cameraCapture.read()
while success:
videoWrite.write(frame)
success, frame = cameraCapture.read()
cameraCapture.release()

捕获摄像头的帧

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 13:39

@Author : Retacn

@Site : 捕获摄像头的帧

@File : videoReadWrite.py

@Software: PyCharm

import cv2

#
cameraCapture=cv2.VideoCapture(0)
FPS=30
size=(int(cameraCapture.get(cv2.CAP_PROP_FRAME_WIDTH))
,int(cameraCapture.get(cv2.CAP_PROP_FRAME_HEIGHT)))
videoWrite=cv2.VideoWriter(‘../test.avi’,cv2.VideoWriter_fourcc(‘I’,’4’,’2’,’0’),FPS,size)

success,frame=cameraCapture.read()
numFramesRemaining=10*FPS-1
while success and numFramesRemaining>0:
videoWrite.write(frame)
success,frame=cameraCapture.read()
numFramesRemaining-=1
cameraCapture.release()

当需要同步一组摄像头或是一个多头摄像头

success0=cameraCapture0.grab()
success1=cameraCapture1.grab()
if success0 and success1:
frame0=cameraCapture0.retrieve()
frame1=cameraCapture1.retrieve()

在窗口显示图像

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 14:09

@Author : Retacn

@Site : 在窗口显示图像

@File : imageShow.py

@Software: PyCharm

import cv2
import numpy as np

img=cv2.imread(‘../test.jpg’)
cv2.imshow(‘Image’,img)
cv2.waitKey()
cv2.destroyAllWindows()

在窗口显示摄像头帧

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/27 14:13

@Author : Retacn

@Site : 在窗口显示摄像头帧

@File : videoCamera.py

@Software: PyCharm

import cv2
import numpy as np

clicked=False
def onMouse(event,x,y,flags,param):
global clicked
if event==cv2.EVENT_LBUTTONUP:#左健抬起
clicked=True

cameraCapture=cv2.VideoCapture(0)
cv2.namedWindow(“VideoWindow”)
cv2.setMouseCallback(‘VideoWindow’,onMouse)

print(‘Showing camera feed,Click window or press any key to stop.’)
success,frame=cameraCapture.read()
while success and cv2.waitKey(1)==-1 and not clicked:
cv2.imshow(‘VideoWindow’,frame)
success,frame=cameraCapture.read()

cv2.destroyWindow(‘VideoWindow’)
cameraCapture.release()

2 cameo项目

3 cameo面向对象的设计

Managers.py文件

示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/28 13:30

@Author : Retacn

@Site : 面向对象的设计

@File : cameo.py

@Software: PyCharm

import cv2
import numpy as np
import time

”’
视频管理
”’
class CaptureManager(object):
def init(self,
capture, #摄像头通道
previewWindowManager=None,#窗口管理器
shouldMirrorPreview=False):#摄像头预览的镜像选项

    self.previewWindowManager=previewWindowManager
    self.shouldMirrorPreview=shouldMirrorPreview

    #定义非公有变量,单下划线开始,为保护变量,只有类对象或子类对象可以访问 protected
    #如果以双下划线开始,为私有成员变量,只有类对象自已可以访问,像private
    self._capture=capture
    self._channel=0
    self._enteredFrame=False
    self._frame=None
    self._imageFilename=None
    self._videoFilename=None
    self._videoEncoding=None
    self._videoWriter=None

    self.startTime=None
    self._framesElapsed=int(0)
    self._fpsEstimate=None

@property
def channel(self):
    return self._channel

@channel.setter
def channel(self,value):
    if self._channel!=value:
        self._channel=value
        self._frame=None

@property
def frame(self):
    if self._enteredFrame and self._frame is None:
        _,self._frame=self._capture.retrieve()
    return self._frame

@property
def isWritingImage(self):
    return self._imageFilename is not None

@property
def isWritingVideo(self):
    return self._videoFilename is not None


#只能同步一帧
def enterFrame(self):

    assert not self._enteredFrame, \
        'previous enterFrame() had no matching exitFrame()'

    if self._capture is not None:
        self._enteredFrame=self._capture.grab()

#可以从当前通道中取得图像,估计帧率,显示图像,执行暂停的请求,向文件中写入图像
def exitFrame(self):
    if self.frame is None:
        self._enteredFrame=False
        return

    #计算帧率
    if self._framesElapsed==0:
        self._startTime=time.time()
    else:
        timeElapsed=time.time()-self._startTime
        self._fpsEstimate=self._framesElapsed/timeElapsed

    self._framesElapsed+=1

    #通过窗体显示图像
    if self.previewWindowManager is not None:
        if self.shouldMirrorPreview:
            mirroredFrame=np.fliplr(self._frame).copy()
            self.previewWindowManager.show(mirroredFrame)
        else:
            self.previewWindowManager.show(self._frame)

    #保存图像文件
    if self.isWritingImage:
        cv2.imwrite(self._imageFilename,self._frame)
        self._imageFilename=None

    #保存视频文件
    self._writeVideoFrame()

    #释放资源
    self._frame=None
    self._enteredFrame=False

#保存图片,公有函数
def writeImage(self,filename):
    self._imageFilename=filename

#开始保存视频,公有函数
def startWritingVideo(self,filename,encoding=cv2.VideoWriter_fourcc('I','4','2','0')):
    self._videoFilename=filename
    self._videoEncoding=encoding

#停止视频写入,公有函数
def stopWritingVideo(self):
    self._videoFilename=None
    self._videoEncoding=None
    self._videoWriter=None

#写入视频帧
def _writeVideoFrame(self):
    if not self.isWritingVideo:
        return

    if self._videoWriter is None:
        fps=self._capture.get(cv2.CAP_PROP_FPS)
        if fps==0.0:
            if self._framesElapsed<20:
                return
            else:
                fps=self._fpsEstimate
        size=(int(self._capture.get(cv2.CAP_PROP_FRAME_WIDTH)),
              int(self._capture.get(cv2.CAP_PROP_FRAME_HEIGHT)))

        self._videoWriter=cv2.VideoWriter(self._videoFilename,
                                          self._videoEncoding,
                                          fps,
                                          size)
    self._videoWriter.write(self._frame)

”’
窗口管理,支持键盘事件
”’
class WindowManager(object):

def __init__(self,
             windowName,#窗体名称
             keypressCallback=None):#按键回调函数
    self.keypressCallback=keypressCallback

    self._windowName=windowName
    self._isWindowCreate=False

#检查窗体是否被创建
@property
def isWindowCreated(self):
    return self._isWindowCreate

#创建窗体
def createWindow(self):
    cv2.namedWindow(self._windowName)
    self._isWindowCreate=True

#显示图像
def show(self,frame):
    cv2.imshow(self._windowName,frame)

#关闭窗体释放资源
def destroyWindow(self):
    cv2.destroyWindow(self._windowName)
    self._isWindowCreate=False

#处理键盘事件
def processEvents(self):
    keycode=cv2.waitKey(1)
    if self.keypressCallback is not None and keycode!=-1:
        keycode&=0xFF #ESC 退出
        self.keypressCallback(keycode)

cameo.py文件
示例代码如下:

!/usr/bin/env python

-- coding: utf-8 --

@Time : 2016/11/28 14:45

@Author : Retacn

@Site : cameo实现,有两种启动方法: run() 和 onkeypress()

@File : cameo.py.py

@Software: PyCharm

import cv2
from Two.cameo.managers import WindowManager,CaptureManager

class Cameo(object):

def __init__(self):
    self._windowManager=WindowManager('Cameo',self.onkeypress)

    self._captureManager=CaptureManager(cv2.VideoCapture(0),self._windowManager,True)

def run(self):
    self._windowManager.createWindow()
    while self._windowManager.isWindowCreated:
        self._captureManager.enterFrame()
        frame=self._captureManager.frame

        self._captureManager.exitFrame()
        self._windowManager.processEvents()

def onkeypress(self,keycode):
    '''
        space-> 载图
        tab->启动和停止视频录制
        esc->退出应用

    :param keycode:
    :return:
    '''
    if keycode==32:#space
        self._captureManager.writeImage('screenshot.png')
    elif keycode==9:#tab
        if not self._captureManager.isWritingVideo:
            self._captureManager.startWritingVideo('screencast.avi')
        else:
            self._captureManager.stopWritingVideo()
    elif keycode==27:#esc
        self._windowManager.destroyWindow()

if name==’main‘:
Cameo().run()