video_capture_set_property :: Quanser C Functions

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video_capture_set_property

Sets properties of a video capture device, such as the brightness or contrast.

Description

The video_capture_set_property function sets properties of a video capture device, such as brightness or contrast. The following table shows the properties that may be set. Note that not all devices support all properties.

Property Code	Description
VIDEO_CAPTURE_PROPERTY_BRIGHTNESS	The brightness of the image from the device.
VIDEO_CAPTURE_PROPERTY_CONTRAST	The contrast of the image from the device.
VIDEO_CAPTURE_PROPERTY_HUE	The hue of the image from the device, which affects the colour of the image.
VIDEO_CAPTURE_PROPERTY_SATURATION	The saturation of the image from the device, which affects the depth of the colour of the image. If the saturation is zero then the image will be grayscale.
VIDEO_CAPTURE_PROPERTY_SHARPNESS	The sharpness of the image from the device, which affects the clarity of edges in the image.
VIDEO_CAPTURE_PROPERTY_GAMMA	The gamma factor of the image from the device, which affects the colour of the image.
VIDEO_CAPTURE_PROPERTY_COLOREFFECT	The colour effect to apply to the image from the device. See the `t_video_capture_color_effect` enumeration for possible values.
VIDEO_CAPTURE_PROPERTY_WHITEBALANCE	The white balance to apply to the image from the device.
VIDEO_CAPTURE_PROPERTY_BACKLIGHTCOMPENSATION	The backlight compensation to use for the image from the device.
VIDEO_CAPTURE_PROPERTY_GAIN	The gain to apply to the image from the device.
VIDEO_CAPTURE_PROPERTY_PAN	How much to pan the camera view from the device.
VIDEO_CAPTURE_PROPERTY_TILT	How much to tilt the camera view from the device.
VIDEO_CAPTURE_PROPERTY_ROLL	How much to roll the camera view from the device.
VIDEO_CAPTURE_PROPERTY_ZOOM	How much to zoom the camera view from the device.
VIDEO_CAPTURE_PROPERTY_EXPOSURE	The exposure to use for the image from the device.
VIDEO_CAPTURE_PROPERTY_IRIS	The aperture to use for the image from the device.
VIDEO_CAPTURE_PROPERTY_FOCUS	The focus to use for the image from the device.

Properties are set using an array of t_video_capture_attribute structures. Each structure contains the following fields:

Field	Data Type	Description
property_code	t_video_capture_property_code	The property which is being set. Valid property codes are listed above.
value	t_double	The value to which to set the attribute, if the attribute is being set manually. The interpretation of this value depends on the field. For enumerations, the value should be an integer value corresponding to the enumeration constant (typically between 1 and N, where N is the number of possibilities). Otherwise, the value should be a fraction between 0 and 1 representing 0% to 100%.
manual	t_boolean	Whether the value is being set manually or will be determined automatically.
is_enumeration	t_boolean	Whether the value is an enumeration or fraction. See the discussion of the field for details.

Prototype

t_error
video_capture_set_property(t_video_capture capture, t_video_capture_attribute * attributes, t_uint num_attributes);

Parameters

t_video_capture capture

A handle to the video capture session, as returned by video_capture_open.

t_video_capture_attribute * attributes

The address of an array of t_video_capture_attribute structures. Each element in the array describes a setting for an attribute of the video capture device, such as the brightness or contrast to use.

Each element of the array is a structure containing four elements, as outlined in the description above.

t_uint num_attributes

The number of attributes in the attributes array.

Return value

The return value is 0 if the attributes are set successfully. Unrecognized property codes are ignored and do not produce an error. Otherwise a negative error code is returned. Error codes are defined in quanser_errors.h. A suitable error message may be retrieved using msg_get_error_message.

Error codes

QERR_INVALID_ARGUMENT

One of the arguments is invalid.

QERR_OUT_OF_MEMORY

There is not enough memory to complete the operation.

Requirements

Include Files	Libraries
quanser_video.h	quanser_media.lib;quanser_communications.lib;quanser_runtime.lib;quanser_common.lib

Examples

t_video_capture_attribute attributes[2];
t_error result;

attributes[0].property_code  = VIDEO_CAPTURE_PROPERTY_BRIGHTNESS;
attributes[0].value          = 0.50; /* 50% brightness */
attributes[0].manual         = true;
attributes[0].is_enumeration = false;

attributes[1].property_code  = VIDEO_CAPTURE_PROPERTY_CONTRAST;
attributes[1].value          = 0.70; /* 70% contrast */
attributes[1].manual         = true;
attributes[1].is_enumeration = false;

result = video_capture_set_property(capture, attributes, ARRAY_LENGTH(attributes));