MimPolarTransform

Board	Supported
Host System	Yes
V4L2	Yes
Clarity UHD	Yes
Concord PoE	No
GenTL	Yes
GevIQ	Yes
GigE Vision	Yes
Indio	No
Iris GTX	Yes
Radient eV-CL	Partial
Rapixo CL	Partial
Rapixo CoF	Partial
Rapixo CXP	Partial
USB3 Vision	Yes

Perform a polar-to-rectangular or rectangular-to-polar transformation on an image or generate LUTs used to perform the transformation.

Syntax

void MimPolarTransform(
    AIL_ID       SrcImageOrDstXLutBufId,  //in
    AIL_ID       DstImageOrYLutBufId,     //out
    AIL_DOUBLE   CenterPosX,              //in
    AIL_DOUBLE   CenterPosY,              //in
    AIL_DOUBLE   StartRadius,             //in
    AIL_DOUBLE   EndRadius,               //in
    AIL_DOUBLE   StartAngle,              //in
    AIL_DOUBLE   EndAngle,                //in
    AIL_INT64    OperationMode,           //in
    AIL_INT64    InterpolationMode,       //in
    AIL_DOUBLE * DstSizeXPtr,             //out
    AIL_DOUBLE * DstSizeYPtr              //out
)

Description

This function performs a rectangular-to-polar or polar-to-rectangular transformation. Alternatively, this function can generate the X- and Y-coordinate LUTs required to perform the transformation usingMimWarp.

For a rectangular-to-polar transformation, the zone of interest to convert is based on a circle centered at CenterPosXand CenterPosY, with the part to convert having the specified start and end radius (StartRadiusandEndRadius) and specified start and end angle (StartAngleandEndAngle), measured with respect to the X-axis of the image.

[Image: mimpolartransform_dia1.png]

The result will be mapped to the destination buffer as follows:

[Image: mimpolartransform_dia2.png]

The increment in angle is determined by the length, in pixels, of the outside arc, calculated as follows:

(endangle - startangle) / arclength.

A polar-to-rectangular transform performs the reverse of the transform described above. It takes a polar buffer and maps it to a rectangular buffer. Use theCenterPosX, CenterPosY, StartAngle, EndAngle, StartRadius, EndRadius parameters to specify where in the destination buffer the contents of the polar buffer will be mapped.

To determine the required size of the destination image or LUT buffer, call the function with DstImageOrYLutBufId set to M_NULL; in this case, DstSizeXPtr and DstSizeYPtr will return the required X- and Y- size of the buffer, respectively. Note that DstSizeXPtr and DstSizeYPtr will return AIL_DOUBLE values; to allocate an appropriate buffer using these values, you should use a ceiling function, such as ceil(), to obtain the X- and Y- sizes as integer (AIL_INT) values.

Parameters

SrcImageOrDstXLutBufId (in, AIL_ID)

Specifies the identifier of the source image buffer or the destination X-coordinate LUT buffer.

DstImageOrYLutBufId (out, AIL_ID)

Specifies the identifier of the destination image buffer or the Y-coordinate LUT buffer.

CenterPosX (in, AIL_DOUBLE)

Specifies the X-coordinate of the circle's center in the rectangular image.

CenterPosY (in, AIL_DOUBLE)

Specifies the Y-coordinate of the circle's center in the rectangular image.

StartRadius (in, AIL_DOUBLE)

Specifies the start radius of the zone of interest in the circle, in pixels.

EndRadius (in, AIL_DOUBLE)

Specifies the end radius of the zone of interest in the circle, in pixels.

StartAngle (in, AIL_DOUBLE)

Specifies the start angle of the zone of interest. The scan starts at this angle.

For specifying the starting angle

Value	Description
-360.0 <= Value <= 720.0	Specifies the start angle.

If the start angle (StartAngle) is less than the end angle (EndAngle), the direction of the scan will be counter clockwise. If the start angle is greater than the end angle, the direction of the scan will be clockwise. There is no maximum span limit between StartAngle and EndAngle. |

EndAngle (in, AIL_DOUBLE)

Specifies the end angle of the zone of interest. The scan ends at this angle.

For specifying the ending angle

Value	Description
-360.0 <= Value <= 720.0	Specifies the end angle.

If the end angle (EndAngle) is greater than the start angle (StartAngle), the direction of the scan will be counter clockwise. If the end angle is less than the start angle, the direction of the scan will be clockwise. There is no maximum span limit between StartAngle and EndAngle. |

OperationMode (in, AIL_INT64)

Specifies the transform to perform.

InterpolationMode (in, AIL_INT64)

Specifies the interpolation mode and overscan used when transforming the source image. When generating the LUTs to perform the transformation, this parameter is ignored and should be set to M_DEFAULT.

For specifying the interpolation mode used in the conversion

Value	Description
M_DEFAULT	Specifies the default interpolation mode and overscan. When transforming the source image, the default is the same as M_NEAREST_NEIGHBOR + M_OVERSCAN_ENABLE.

When only generating the LUTs to perform the transformation, this is the only possible value. | | M_BICUBIC | Specifies bicubic interpolation. The new value is determined by taking a weighted average of the 16 values (4x4) that surround the source point. Note that the sum of the weights used for bicubic interpolation might be greater than one. If this occurs and the result reflects an overflow or underflow, the result is saturated according to the depth and data type of the destination buffer. | | M_BILINEAR | Specifies bilinear interpolation. The new value is determined by taking a weighted average of the 4 values (2x2) that surround the source point. | | M_NEAREST_NEIGHBOR | Specifies nearest neighbor interpolation. The new value is that of the pixel closest to the source point. |

For specifying how to determine the value of a destination pixel when its associated point falls outside the source buffer

Value	Description
M_OVERSCAN_CLEAR	Sets the destination pixel to 0.
M_OVERSCAN_DISABLE	Leaves the destination pixel as is.
M_OVERSCAN_ENABLE (default)	Uses pixels from the source buffer's ancestor buffer. If the source buffer is not a child buffer or if the point falls outside the ancestor buffer, leave the destination pixel as is.
M_OVERSCAN_FAST	Specifies that Aurora Imaging Library will automatically select the overscan that optimizes speed, according to the specified operation and the target system. The overscan could be hardware-specific thereby having a different behavior than the other supported overscan modes.

Note that when using M_OVERSCAN_FAST, the destination pixels in the overscan area are undefined. The pixels can therefore contain different values from one function call to the next, even if the function's parameter values are the same. |

DstSizeXPtr *(out, AIL_DOUBLE)

Specifies the address of the variable in which the required width of the destination buffer is written. If you don't need this information, set this parameter to M_NULL.

DstSizeYPtr *(out, AIL_DOUBLE)

Specifies the address of the variable in which the required height of the destination buffer is written. If you don't need this information, set this parameter to M_NULL.

Parameter Associations

For selecting the Operation Mode

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M_POLAR_TO_RECTANGULAR

Performs a polar-to-rectangular transformation.

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M_POLAR_TO_RECTANGULAR_LUT

Generates X- and Y-coordinate LUTs for use with MimWarpto perform the specified polar-to-rectangular transformation.

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M_RECTANGULAR_TO_POLAR

Performs a rectangular-to-polar transformation.

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M_RECTANGULAR_TO_POLAR_LUT

Generates X- and Y-coordinate LUTs for use with MimWarpto perform the specified rectangular-to-polar transformation.

Combination Constants — For generating LUTs

Optional.

Usage: You can add one of the following values to the above-mentioned values to specify the number of fractional bits in the coordinates of the source point.

Value	Description
M_FIXED_POINT + n	Specifies the number of fractional bits for the source point (_x_ <sub>s</sub>, _y_ <sub>s</sub>). To do so, add the define M_FIXED_POINT + n to M_POLAR_TO_RECTANGULAR_LUT or M_RECTANGULAR_TO_POLAR_LUTwhere _n_ >= 0. If nothing is added to M_POLAR_TO_RECTANGULAR_LUT or M_RECTANGULAR_TO_POLAR_LUT, it is assumed that there are no fractional bits in the coordinates of the source point.