为了取得好的图片效果，我们需要设置摄像头的参数。

假如摄像流为 cap， 那么设置参数是cap.set(参数编号，参数)

获取参数值的函数是  cap.get(参数编号)

看一段摄像头参数设置读取的例子吧，代码里先设置3个参数，然后再读取这3个参数。

import cv2

#选择摄像头号，一般从 0 开始

cap = cv2.VideoCapture(0)

#先设置参数，然后读取参数

cap.set(3,1280)

cap.set(4,1024)

cap.set(15, 0.1)

print("width={}".format(cap.get(3)))

print("height={}".format(cap.get(4)))

print("exposure={}".format(cap.get(15)))

while True:

ret, img = cap.read()

cv2.imshow("input", img)

# 按 ESC 键退出

key = cv2.waitKey(10)

if key == 27:

break

cv2.destroyAllWindows()

cv2.VideoCapture(0).release()

我的程序运行结果是：

width=1280.0

height=720.0

exposure=-1.0

宽，高，设置有效，而曝光量设置返回无效。

摄像头有哪些参数可以设置呢？参数编号的对应关系怎么样，请看下面列表。

0. CV_CAP_PROP_POS_MSEC Current position of the video file in milliseconds.

1. CV_CAP_PROP_POS_FRAMES 0-based index of the frame to be decoded/captured next.

2. CV_CAP_PROP_POS_AVI_RATIO Relative position of the video file

3. CV_CAP_PROP_FRAME_WIDTH Width of the frames in the video stream.

4. CV_CAP_PROP_FRAME_HEIGHT Height of the frames in the video stream.

5. CV_CAP_PROP_FPS Frame rate.

6. CV_CAP_PROP_FOURCC 4-character code of codec.

7. CV_CAP_PROP_FRAME_COUNT Number of frames in the video file.

8. CV_CAP_PROP_FORMAT Format of the Mat objects returned by retrieve() .

9. CV_CAP_PROP_MODE Backend-specific value indicating the current capture mode.

10. CV_CAP_PROP_BRIGHTNESS Brightness of the image (only for cameras).

11. CV_CAP_PROP_CONTRAST Contrast of the image (only for cameras).

12. CV_CAP_PROP_SATURATION Saturation of the image (only for cameras).

13. CV_CAP_PROP_HUE Hue of the image (only for cameras).

14. CV_CAP_PROP_GAIN Gain of the image (only for cameras).

15. CV_CAP_PROP_EXPOSURE Exposure (only for cameras).

16. CV_CAP_PROP_CONVERT_RGB Boolean flags indicating whether images should be converted to RGB.

17. CV_CAP_PROP_WHITE_BALANCE Currently unsupported

18. CV_CAP_PROP_RECTIFICATION Rectification flag for stereo cameras (note: only supported by DC1394 v 2.x backend currently)

这里是可能可以设置的参数，摄像头不一样，有些参数可能是不能设置的。

一般读取返回-1 的就是无效，下面再看一段检测有效无效的代码，就是上面代码改的

import cv2

#选择摄像头号，一般从 0 开始

cap = cv2.VideoCapture(0)

#先设置参数，然后读取参数

for i in range(47):

print("No.={} parameter={}".format(i,cap.get(i)))

while True:

ret, img = cap.read()

cv2.imshow("input", img)

# 按 ESC 键退出

key = cv2.waitKey(10)

if key == 27:

break

cv2.destroyAllWindows()

cv2.VideoCapture(0).release()

运行结果是：

0=0.0

1=0.0

2=-1.0

3=1280.0

4=720.0

5=30.0

6=842094158.0

7=-1.0

8=-1.0

9=0.0

10=0.0

11=0.0

12=64.0

13=0.0

14=0.0

15=-1.0

16=1.0

17=-1.0

18=-1.0

19=-1.0

20=2.0

21=-1.0

22=100.0

23=4600.0

24=-1.0

25=-1.0

26=-1.0

27=-1.0

28=-1.0

29=-1.0

30=-1.0

31=-1.0

32=3.0

33=-1.0

34=-1.0

35=-1.0

36=-1.0

37=-1.0

38=-1.0

39=-1.0

40=1.0

41=1.0

42=1400.0

43=-1.0

44=-1.0

45=-1.0

46=-1.0

可以看到我的摄像头哪些参数可以设置，不为-1的。

在程序中编号很容易弄错，可以用如下方式比较好看一点，也不容易出错。

cap.set(cv2.CAP_PROP_FRAME_WIDTH,1280)

cap.set(cv2.CAP_PROP_FRAME_HEIGHT,1024)

cap.set(cv2.CAP_PROP_EXPOSURE, 0.1)

上面表不完整，但基本都包括了我们看看现在opencv 里面怎么说的：

https://github.com/opencv/opencv/blob/master/modules/videoio/include/opencv2/videoio.hpp

enum VideoCaptureProperties {

CAP_PROP_POS_MSEC =0, //!< Current position of the video file in milliseconds.

CAP_PROP_POS_FRAMES =1, //!< 0-based index of the frame to be decoded/captured next.

CAP_PROP_POS_AVI_RATIO =2, //!< Relative position of the video file: 0=start of the film, 1=end of the film.

CAP_PROP_FRAME_WIDTH =3, //!< Width of the frames in the video stream.

CAP_PROP_FRAME_HEIGHT =4, //!< Height of the frames in the video stream.

CAP_PROP_FPS =5, //!< Frame rate.

CAP_PROP_FOURCC =6, //!< 4-character code of codec. see VideoWriter::fourcc .

CAP_PROP_FRAME_COUNT =7, //!< Number of frames in the video file.

CAP_PROP_FORMAT =8, //!< Format of the %Mat objects returned by VideoCapture::retrieve().

CAP_PROP_MODE =9, //!< Backend-specific value indicating the current capture mode.

CAP_PROP_BRIGHTNESS =10, //!< Brightness of the image (only for those cameras that support).

CAP_PROP_CONTRAST =11, //!< Contrast of the image (only for cameras).

CAP_PROP_SATURATION =12, //!< Saturation of the image (only for cameras).

CAP_PROP_HUE =13, //!< Hue of the image (only for cameras).

CAP_PROP_GAIN =14, //!< Gain of the image (only for those cameras that support).

CAP_PROP_EXPOSURE =15, //!< Exposure (only for those cameras that support).

CAP_PROP_CONVERT_RGB =16, //!< Boolean flags indicating whether images should be converted to RGB.

CAP_PROP_WHITE_BALANCE_BLUE_U =17, //!< Currently unsupported.

CAP_PROP_RECTIFICATION =18, //!< Rectification flag for stereo cameras (note: only supported by DC1394 v 2.x backend currently).

CAP_PROP_MONOCHROME =19,

CAP_PROP_SHARPNESS =20,

CAP_PROP_AUTO_EXPOSURE =21, //!< DC1394: exposure control done by camera, user can adjust reference level using this feature.

CAP_PROP_GAMMA =22,

CAP_PROP_TEMPERATURE =23,

CAP_PROP_TRIGGER =24,

CAP_PROP_TRIGGER_DELAY =25,

CAP_PROP_WHITE_BALANCE_RED_V =26,

CAP_PROP_ZOOM =27,

CAP_PROP_FOCUS =28,

CAP_PROP_GUID =29,

CAP_PROP_ISO_SPEED =30,

CAP_PROP_BACKLIGHT =32,

CAP_PROP_PAN =33,

CAP_PROP_TILT =34,

CAP_PROP_ROLL =35,

CAP_PROP_IRIS =36,

CAP_PROP_SETTINGS =37, //!< Pop up video/camera filter dialog (note: only supported by DSHOW backend currently. The property value is ignored)

CAP_PROP_BUFFERSIZE =38,

CAP_PROP_AUTOFOCUS =39,

CAP_PROP_SAR_NUM =40, //!< Sample aspect ratio: num/den (num)

CAP_PROP_SAR_DEN =41, //!< Sample aspect ratio: num/den (den)

CAP_PROP_BACKEND =42, //!< Current backend (enum VideoCaptureAPIs). Read-only property

CAP_PROP_CHANNEL =43, //!< Video input or Channel Number (only for those cameras that support)

CAP_PROP_AUTO_WB =44, //!< enable/ disable auto white-balance

CAP_PROP_WB_TEMPERATURE=45, //!< white-balance color temperature

#ifndef CV_DOXYGEN

CV__CAP_PROP_LATEST

#endif

};

其实参数取值范围很重要，看来我还是要查找资料。下面是别人的一个例子。

capture.set(CV_CAP_PROP_FPS, 30);//帧率 帧/秒

capture.set(CV_CAP_PROP_BRIGHTNESS, 1);//亮度

capture.set(CV_CAP_PROP_CONTRAST,40);//对比度 40

capture.set(CV_CAP_PROP_SATURATION, 50);//饱和度 50

capture.set(CV_CAP_PROP_HUE, 50);//色调 50

capture.set(CV_CAP_PROP_EXPOSURE, 50);//曝光 50 获取摄像头参数

要核实参数范围，我们用一个现成的软件，比如windows 的相机，或者AMcap，linux下的guvcview，cheese。

在设置好参数后，我们的python 程序获取他们的参数，是个比较好的办法。

然后用python运行获取所有参数:

for i in range(49):

if abs(cap.get(i)+1)>0.001:

print("{}.parameter={}".format(i,cap.get(i)))

我的运行结果如下：

ipdb> 0.parameter=0.0

1.parameter=0.0

3.parameter=1280.0

4.parameter=720.0

5.parameter=30.0

6.parameter=842094158.0

9.parameter=0.0

10.parameter=0.0

11.parameter=0.0

12.parameter=64.0

13.parameter=0.0

14.parameter=0.0

16.parameter=1.0

20.parameter=2.0

22.parameter=100.0

23.parameter=4600.0

32.parameter=3.0

40.parameter=1.0

41.parameter=1.0

42.parameter=1400.0

在不知道参数范围的情况下调整参数比较盲目。

下面看我用Amp 的参数调整对话框，大致可以看出参数调整的范围。