VCAP Class Reference

API for the Video Capture driver. More...

Detailed Description

• ID: vcap
• Name: Video Frame Capture and Image Save Utility
• Category: video

This UPM module captures a still frame from a Linux V4L device, such as a USB webcam, and and then allows you to save it as a JPEG image into a file.

The camera and driver in use must support streaming, mmap-able buffers and must provide data in YUYV format. This should encompass most video cameras out there. It has been tested with a few off the shelf cameras without any problems.

    string defaultDev = "/dev/video0";

    // if an argument was specified, use it as the device instead
    if (argc > 1)
        defaultDev = string(argv[1]);

    cout << "Using device " << defaultDev << endl;
    cout << "Initializing..." << endl;

    // Instantiate an VCAP instance, using the specified video device
    upm::VCAP sensor(defaultDev);

    // enable some debug/verbose output
    sensor.setDebug(true);

    // This is just a hint.  The kernel can change this to a lower
    // resolution that the hardware supports.  Use getWidth() and
    // getHeight() methods to see what the kernel actually chose if you
    // care.
    sensor.setResolution(1920, 1080);

    // capture an image
    sensor.captureImage();

    // convert and save it as a jpeg
    sensor.saveImage("video-img1.jpg");

    cout << "Exiting..." << endl;

Public Member Functions
	VCAP (std::string videoDev=VCAP_DEFAULT_VIDEODEV)
	~VCAP ()
bool	setResolution (int width, int height)
bool	captureImage ()
bool	saveImage (std::string filename=VCAP_DEFAULT_OUTPUTFILE)
int	getWidth () const
int	getHeight () const
void	setJPGQuality (unsigned int quality)
int	getJPGQuality () const
void	setDebug (bool enable)

Protected Member Functions
bool	initVideoDevice ()
bool	checkCapabilities ()
bool	YUYV2JPEG (FILE *file)
bool	allocBuffer ()
void	releaseBuffer ()
bool	doCaptureImage ()

Constructor & Destructor Documentation

VCAP

(

std::string

videoDev = VCAP_DEFAULT_VIDEODEV

)

VCAP object constructor

Parameters

videoDev

The path to the video device, default is /dev/video0.

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~VCAP

(

)

VCAP object destructor

Member Function Documentation

bool setResolution	(	int	width,
		int	height
	)

Set the desired resolution of the output image. Note, this is a hint to the underlying video driver. The video driver is free to lower the specified resolution if the hardware cannot support it. You can use getHeight() and getWidth() after calling this method to see what the video driver chose.

Parameters

width	The desired width of the image.
width	The desired height of the image.

Returns

true if the operation succeeded, false otherwise.

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bool captureImage

(

)

Capture an image from the camera.

Returns

true if the operation succeeded, false otherwise.

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bool saveImage

(

std::string

filename = VCAP_DEFAULT_OUTPUTFILE

)

Save the captured image (created with captureImage()) to a file in JPEG format. The file will be overwritten if it already exists.

Parameters

filename

The name of the file in which to store the image.

Returns

true if the operation succeeded, false otherwise.

int getWidth ( ) const

inline

Return the current width of the image. You can use this method to determine if the video driver downgraded it after a call to setResolution().

Returns

true Current width of capture.

int getHeight ( ) const

inline

Return the current height of the image. You can use this method to determine if the video driver downgraded it after a call to setResolution().

Returns

true Current height of capture.

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void setJPGQuality

(

unsigned int

quality

)

Set the JPEG quality.

Parameters

quality

A number between 0-100, with higher numbers meaning higher quality. Numbers less than 0 will be clamped to 0, numbers higher than 100 will be clamped to 100.

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int getJPGQuality ( ) const

inline

Get the current JPEG quality setting.

Returns

the current JPEG quality setting.

void setDebug ( bool  enable )

inline

Enable or disable debugging output.

Parameters

enable

true to enable debugging, false otherwise

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The documentation for this class was generated from the following files:

• src/vcap/vcap.hpp
• src/vcap/vcap.cxx