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libcamera
v0.4.0
Supporting cameras in Linux since 2019
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Namespace for libcamera properties. More...
Namespaces | |
| draft | |
| Namespace for draft properties. | |
Enumerations | |
| enum | LocationEnum { CameraLocationFront = 0, CameraLocationBack = 1, CameraLocationExternal = 2 } |
| Supported Location values. More... | |
Variables | |
| const ControlIdMap | properties |
| List of all supported libcamera properties. | |
| const std::array< const ControlValue, 3 > | LocationValues |
| List of all Location supported values. | |
| const std::map< std::string, int32_t > | LocationNameValueMap |
| Map of all Location supported value names (in std::string format) to value. | |
| const Control< int32_t > | Location |
| Camera mounting location. | |
| const Control< int32_t > | Rotation |
| The camera physical mounting rotation. It is expressed as the angular difference in degrees between two reference systems, one relative to the camera module, and one defined on the external world scene to be captured when projected on the image sensor pixel array. More... | |
| const Control< std::string > | Model |
| The model name shall to the extent possible describe the sensor. For most devices this is the model name of the sensor. While for some devices the sensor model is unavailable as the sensor or the entire camera is part of a larger unit and exposed as a black-box to the system. In such cases the model name of the smallest device that contains the camera sensor shall be used. More... | |
| const Control< Size > | UnitCellSize |
| The pixel unit cell physical size, in nanometers. More... | |
| const Control< Size > | PixelArraySize |
| The camera sensor pixel array readable area vertical and horizontal sizes, in pixels. More... | |
| const Control< Span< const Rectangle > > | PixelArrayOpticalBlackRectangles |
| The pixel array region(s) which contain optical black pixels considered valid for calibration purposes. More... | |
| const Control< Span< const Rectangle > > | PixelArrayActiveAreas |
| The PixelArrayActiveAreas property defines the (possibly multiple and overlapping) portions of the camera sensor readable pixel matrix which are considered valid for image acquisition purposes. More... | |
| const Control< Rectangle > | ScalerCropMaximum |
| The maximum valid rectangle for the controls::ScalerCrop control. This reflects the minimum mandatory cropping applied in the camera sensor and the rest of the pipeline. Just as the ScalerCrop control, it defines a rectangle taken from the sensor's active pixel array. More... | |
| const Control< float > | SensorSensitivity |
| The relative sensitivity of the chosen sensor mode. More... | |
| const Control< Span< const int64_t > > | SystemDevices |
| A list of integer values of type dev_t denoting the major and minor device numbers of the underlying devices used in the operation of this camera. More... | |
Namespace for libcamera properties.
Supported Location values.
| libcamera::properties::Model |
The model name shall to the extent possible describe the sensor. For most devices this is the model name of the sensor. While for some devices the sensor model is unavailable as the sensor or the entire camera is part of a larger unit and exposed as a black-box to the system. In such cases the model name of the smallest device that contains the camera sensor shall be used.
The model name is not meant to be a camera name displayed to the end-user, but may be combined with other camera information to create a camera name.
The model name is not guaranteed to be unique in the system nor is it guaranteed to be stable or have any other properties required to make it a good candidate to be used as a permanent identifier of a camera.
The model name shall describe the camera in a human readable format and shall be encoded in ASCII.
Example model names are 'ov5670', 'imx219' or 'Logitech Webcam C930e'.
| libcamera::properties::PixelArrayActiveAreas |
The PixelArrayActiveAreas property defines the (possibly multiple and overlapping) portions of the camera sensor readable pixel matrix which are considered valid for image acquisition purposes.
This property describes an arbitrary number of overlapping rectangles, with each rectangle representing the maximum image size that the camera sensor can produce for a particular aspect ratio. They are defined relatively to the PixelArraySize rectangle.
When multiple rectangles are reported, they shall be ordered from the tallest to the shortest.
Example 1 A camera sensor which only produces images in the 4:3 image resolution will report a single PixelArrayActiveAreas rectangle, from which all other image formats are obtained by either cropping the field-of-view and/or applying pixel sub-sampling techniques such as pixel skipping or binning.
PixelArraySize.width
/----------------/
x1 x2
(0,0)-> +-o------------o-+ /
y1 o +------------+ | |
| |////////////| | |
| |////////////| | | PixelArraySize.height
| |////////////| | |
y2 o +------------+ | |
+----------------+ /
The property reports a single rectangle
PixelArrayActiveAreas = (x1, y1, x2 - x1 + 1, y2 - y1 + 1)
Example 2 A camera sensor which can produce images in different native resolutions will report several overlapping rectangles, one for each natively supported resolution.
PixelArraySize.width
/------------------/
x1 x2 x3 x4
(0,0)-> +o---o------o---o+ /
y1 o +------+ | |
| |//////| | |
y2 o+---+------+---+| |
||///|//////|///|| | PixelArraySize.height
y3 o+---+------+---+| |
| |//////| | |
y4 o +------+ | |
+----+------+----+ /
The property reports two rectangles
PixelArrayActiveAreas = ((x2, y1, x3 - x2 + 1, y4 - y1 + 1),
(x1, y2, x4 - x1 + 1, y3 - y2 + 1))
The first rectangle describes the maximum field-of-view of all image formats in the 4:3 resolutions, while the second one describes the maximum field of view for all image formats in the 16:9 resolutions.
Multiple rectangles shall only be reported when the sensor can't capture the pixels in the corner regions. If all the pixels in the (x1,y1) - (x4,y4) area can be captured, the PixelArrayActiveAreas property shall contains the single rectangle (x1,y1) - (x4,y4).
| libcamera::properties::PixelArrayOpticalBlackRectangles |
The pixel array region(s) which contain optical black pixels considered valid for calibration purposes.
This property describes the position and size of optical black pixel regions in the raw data buffer as stored in memory, which might differ from their actual physical location in the pixel array matrix.
It is important to note, in fact, that camera sensors might automatically reorder or skip portions of their pixels array matrix when transmitting data to the receiver. For instance, a sensor may merge the top and bottom optical black rectangles into a single rectangle, transmitted at the beginning of the frame.
The pixel array contains several areas with different purposes, interleaved by lines and columns which are said not to be valid for capturing purposes. Invalid lines and columns are defined as invalid as they could be positioned too close to the chip margins or to the optical black shielding placed on top of optical black pixels.
PixelArraySize.width
/----------------------------------------------/
x1 x2
+--o---------------------------------------o---+ /
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
y1 oIIOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOII| |
|IIOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOII| |
|IIOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOII| |
y2 oIIOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOII| |
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
y3 |IIOOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOOII| |
|IIOOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOOII| | PixelArraySize.height
|IIOOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOOII| |
... ... ... ... ...
... ... ... ... ...
y4 |IIOOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOOII| |
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
|IIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII| |
+----------------------------------------------+ /
The readable pixel array matrix is composed by 2 invalid lines (I) 4 lines of valid optical black pixels (O) 2 invalid lines (I) n lines of valid pixel data (P) 2 invalid lines (I)
And the position of the optical black pixel rectangles is defined by
PixelArrayOpticalBlackRectangles = {
{ x1, y1, x2 - x1 + 1, y2 - y1 + 1 },
{ x1, y3, 2, y4 - y3 + 1 },
{ x2, y3, 2, y4 - y3 + 1 },
};
If the camera, when capturing the full pixel array matrix, automatically skips the invalid lines and columns, producing the following data buffer, when captured to memory
PixelArraySize.width
/----------------------------------------------/
x1
+--------------------------------------------o-+ /
|OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO| |
|OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO| |
|OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO| |
|OOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOO| |
y1 oOOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOO| |
|OOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOO| |
|OOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOO| | PixelArraySize.height
... ... ... ... ... |
... ... ... ... ... |
|OOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOO| |
|OOPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPPOO| |
+----------------------------------------------+ /
then the invalid lines and columns should not be reported as part of the PixelArraySize property in first place.
In this case, the position of the black pixel rectangles will be
PixelArrayOpticalBlackRectangles = {
{ 0, 0, y1 + 1, PixelArraySize[0] },
{ 0, y1, 2, PixelArraySize[1] - y1 + 1 },
{ x1, y1, 2, PixelArraySize[1] - y1 + 1 },
};
| libcamera::properties::PixelArraySize |
The camera sensor pixel array readable area vertical and horizontal sizes, in pixels.
The PixelArraySize property defines the size in pixel units of the readable part of full pixel array matrix, including optical black pixels used for calibration, pixels which are not considered valid for capture and active pixels containing valid image data.
The property describes the maximum size of the raw data captured by the camera, which might not correspond to the physical size of the sensor pixel array matrix, as some portions of the physical pixel array matrix are not accessible and cannot be transmitted out.
For example, let's consider a pixel array matrix assembled as follows
+--------------------------------------------------+ |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx| |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| ... ... ... ... ... ... ... ... ... ... |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDxx| |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx| |xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx| +--------------------------------------------------+
starting with two lines of non-readable pixels (x), followed by N lines of readable data (D) surrounded by two columns of non-readable pixels on each side, and ending with two more lines of non-readable pixels. Only the readable portion is transmitted to the receiving side, defining the sizes of the largest possible buffer of raw data that can be presented to applications.
PixelArraySize.width /----------------------------------------------/ +----------------------------------------------+ / |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | PixelArraySize.height ... ... ... ... ... ... ... ... ... ... |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | |DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD| | +----------------------------------------------+ /
This defines a rectangle whose top-left corner is placed in position (0, 0) and whose vertical and horizontal sizes are defined by this property. All other rectangles that describe portions of the pixel array, such as the optical black pixels rectangles and active pixel areas, are defined relatively to this rectangle.
All the coordinates are expressed relative to the default sensor readout direction, without any transformation (such as horizontal and vertical flipping) applied. When mapping them to the raw pixel buffer, applications shall take any configured transformation into account.
| libcamera::properties::Rotation |
The camera physical mounting rotation. It is expressed as the angular difference in degrees between two reference systems, one relative to the camera module, and one defined on the external world scene to be captured when projected on the image sensor pixel array.
A camera sensor has a 2-dimensional reference system 'Rc' defined by its pixel array read-out order. The origin is set to the first pixel being read out, the X-axis points along the column read-out direction towards the last columns, and the Y-axis along the row read-out direction towards the last row.
A typical example for a sensor with a 2592x1944 pixel array matrix observed from the front is
2591 X-axis 0
<------------------------+ 0
.......... ... ..........!
.......... ... ..........! Y-axis
... !
.......... ... ..........!
.......... ... ..........! 1943
V
The external world scene reference system 'Rs' is a 2-dimensional reference system on the focal plane of the camera module. The origin is placed on the top-left corner of the visible scene, the X-axis points towards the right, and the Y-axis points towards the bottom of the scene. The top, bottom, left and right directions are intentionally not defined and depend on the environment in which the camera is used.
A typical example of a (very common) picture of a shark swimming from left to right, as seen from the camera, is
0 X-axis
0 +------------------------------------->
!
!
!
! |\____)\___
! ) _____ __`<
! |/ )/
!
!
!
V
Y-axis
With the reference system 'Rs' placed on the camera focal plane.
¸.·˙!
¸.·˙ !
_ ¸.·˙ !
+-/ \-+¸.·˙ !
| (o) | ! Camera focal plane
+-----+˙·.¸ !
˙·.¸ !
˙·.¸ !
˙·.¸!
When projected on the sensor's pixel array, the image and the associated reference system 'Rs' are typically (but not always) inverted, due to the camera module's lens optical inversion effect.
Assuming the above represented scene of the swimming shark, the lens inversion projects the scene and its reference system onto the sensor pixel array, seen from the front of the camera sensor, as follow
Y-axis
^
!
!
!
! |\_____)\__
! ) ____ ___.<
! |/ )/
!
!
!
0 +------------------------------------->
0 X-axis
Note the shark being upside-down.
The resulting projected reference system is named 'Rp'.
The camera rotation property is then defined as the angular difference in the counter-clockwise direction between the camera reference system 'Rc' and the projected scene reference system 'Rp'. It is expressed in degrees as a number in the range [0, 360[.
Examples
0 degrees camera rotation
Y-Rp
^
Y-Rc !
^ !
! !
! !
! !
! !
! !
! !
! !
! 0 +------------------------------------->
! 0 X-Rp
0 +------------------------------------->
0 X-Rc
X-Rc 0
<------------------------------------+ 0
X-Rp 0 !
<------------------------------------+ 0 !
! !
! !
! !
! !
! !
! !
! !
! V
! Y-Rc
V
Y-Rp
90 degrees camera rotation
0 Y-Rc
0 +-------------------->
! Y-Rp
! ^
! !
! !
! !
! !
! !
! !
! !
! !
! !
! 0 +------------------------------------->
! 0 X-Rp
!
!
!
!
V
X-Rc
180 degrees camera rotation
0
<------------------------------------+ 0
X-Rc !
Y-Rp !
^ !
! !
! !
! !
! !
! !
! !
! V
! Y-Rc
0 +------------------------------------->
0 X-Rp
270 degrees camera rotation
0 Y-Rc
0 +-------------------->
! 0
! <-----------------------------------+ 0
! X-Rp !
! !
! !
! !
! !
! !
! !
! !
! !
! V
! Y-Rp
!
!
!
!
V
X-Rc
Example one - Webcam
A camera module installed on the user facing part of a laptop screen casing used for video calls. The captured images are meant to be displayed in landscape mode (width > height) on the laptop screen.
The camera is typically mounted upside-down to compensate the lens optical inversion effect.
Y-Rp
Y-Rc ^
^ !
! !
! ! |\_____)\__
! ! ) ____ ___.<
! ! |/ )/
! !
! !
! !
! 0 +------------------------------------->
! 0 X-Rp
0 +------------------------------------->
0 X-Rc
The two reference systems are aligned, the resulting camera rotation is 0 degrees, no rotation correction needs to be applied to the resulting image once captured to memory buffers to correctly display it to users.
+--------------------------------------+
! !
! !
! !
! |\____)\___ !
! ) _____ __`< !
! |/ )/ !
! !
! !
! !
+--------------------------------------+
If the camera sensor is not mounted upside-down to compensate for the lens optical inversion, the two reference systems will not be aligned, with 'Rp' being rotated 180 degrees relatively to 'Rc'.
X-Rc 0
<------------------------------------+ 0
!
Y-Rp !
^ !
! !
! |\_____)\__ !
! ) ____ ___.< !
! |/ )/ !
! !
! !
! V
! Y-Rc
0 +------------------------------------->
0 X-Rp
The image once captured to memory will then be rotated by 180 degrees
+--------------------------------------+
! !
! !
! !
! __/(_____/| !
! >.___ ____ ( !
! \( \| !
! !
! !
! !
+--------------------------------------+
A software rotation correction of 180 degrees should be applied to correctly display the image.
+--------------------------------------+
! !
! !
! !
! |\____)\___ !
! ) _____ __`< !
! |/ )/ !
! !
! !
! !
+--------------------------------------+
Example two - Phone camera
A camera installed on the back side of a mobile device facing away from the user. The captured images are meant to be displayed in portrait mode (height > width) to match the device screen orientation and the device usage orientation used when taking the picture.
The camera sensor is typically mounted with its pixel array longer side aligned to the device longer side, upside-down mounted to compensate for the lens optical inversion effect.
0 Y-Rc
0 +-------------------->
! Y-Rp
! ^
! !
! !
! !
! ! |\_____)\__
! ! ) ____ ___.<
! ! |/ )/
! !
! !
! !
! 0 +------------------------------------->
! 0 X-Rp
!
!
!
!
V
X-Rc
The two reference systems are not aligned and the 'Rp' reference system is rotated by 90 degrees in the counter-clockwise direction relatively to the 'Rc' reference system.
The image once captured to memory will be rotated.
+-------------------------------------+
| _ _ |
| \ / |
| | | |
| | | |
| | > |
| < | |
| | | |
| . |
| V |
+-------------------------------------+
A correction of 90 degrees in counter-clockwise direction has to be applied to correctly display the image in portrait mode on the device screen.
+--------------------+
| |
| |
| |
| |
| |
| |
| |\____)\___ |
| ) _____ __`< |
| |/ )/ |
| |
| |
| |
| |
| |
+--------------------+
| libcamera::properties::ScalerCropMaximum |
The maximum valid rectangle for the controls::ScalerCrop control. This reflects the minimum mandatory cropping applied in the camera sensor and the rest of the pipeline. Just as the ScalerCrop control, it defines a rectangle taken from the sensor's active pixel array.
This property is valid only after the camera has been successfully configured and its value may change whenever a new configuration is applied.
| libcamera::properties::SensorSensitivity |
The relative sensitivity of the chosen sensor mode.
Some sensors have readout modes with different sensitivities. For example, a binned camera mode might, with the same exposure and gains, produce twice the signal level of the full resolution readout. This would be signalled by the binned mode, when it is chosen, indicating a value here that is twice that of the full resolution mode. This value will be valid after the configure method has returned successfully.
| libcamera::properties::SystemDevices |
A list of integer values of type dev_t denoting the major and minor device numbers of the underlying devices used in the operation of this camera.
Different cameras may report identical devices.
| libcamera::properties::UnitCellSize |
The pixel unit cell physical size, in nanometers.
The UnitCellSize properties defines the horizontal and vertical sizes of a single pixel unit, including its active and non-active parts. In other words, it expresses the horizontal and vertical distance between the top-left corners of adjacent pixels.
The property can be used to calculate the physical size of the sensor's pixel array area and for calibration purposes.
1.8.13