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MimEdgeDetect


Function Map
Syntax
Description
Parameters
- SrcImageBufId
- DstIntensityImageBufId
- DstAngleImageBufId
- KernelId
Table: For specifying the filter to use
+ combination: For specifying the overscan setting
- ControlFlag
Table: For specifying how to perform the operation
- Threshold
Compilation information
Synopsis
Perform a specific edge detection operation and produce a gradient intensity and/or gradient angle image.
Syntax
void MimEdgeDetect(
MIL_ID SrcImageBufId, //in
MIL_ID DstIntensityImageBufId, //in
MIL_ID DstAngleImageBufId, //in
MIL_ID KernelId, //in
MIL_INT64 ControlFlag, //in
MIL_INT Threshold //in
)
Description

This function performs an edge detection operation on the specified source image, using the specified filter. It produces a gradient intensity image and/or a gradient angle image in the specified image buffer(s). If one of the destination images is not required, specify M_NULL as its image buffer identifier.

For an unsigned destination buffer, the angle is returned from 0° to 360° (counter-clockwise) and mapped to the entire range of the destination buffer. For example, for an 8-bit unsigned buffer, the angles of 0°, 90°, 180°, and 270° map to 0, 64, 128, and 192, respectively. For a signed destination buffer, mapping is done in both the positive and negative range of the buffer and represents angle values from -180° to 180°. For example, for an 8-bit signed buffer, the angles of -180°, -90°, 0°, and 90° map to -128, -64, 0 and 64, respectively.

This function can also be performed on a floating-point buffer. However, the results are not mapped and are returned in the range of 0° to 360°. The degree of precision is equal to the precision of the floating-point buffer for regular computation or to +/- 0.4° for fast computation. The value for undefined results is the maximum positive value of the floating-point buffer.

You can perform the operation using a combination of fast and full gradient and angle computations.

Type of computation

Description of computation

Full gradient computation

Gradient = sqrt(GradientX*GradientX + GradientY*GradientY)

Fast gradient computation

Gradient = (abs(GradientX) + abs(GradientY))/2

Full angle computation

Angle = arctan(-GradientY/GradientX)

Fast angle computation

The fast angle approximation is based on the same equation as the full angle computation; however, the value is determined from a LUT mapping.
Note that this function reference has not been updated for a MIL system added during a MIL update. Refer to the MIL system's release note to see which MIL system’s documentation you should use in its place and any possible differences.
Parameters
This function is not supported on the selected boards.
This function reference has not been updated for the selected MIL system. To show the content of this page, choose a second MIL system; refer to the MIL system's release note to see which MIL system’s documentation to choose and any possible differences.
Parameters
SrcImageBufId

Specifies the identifier of the source of the operation. This parameter must be given an image buffer identifier.

This image buffer must not have a region of interest (ROI) associated with it. Using an image buffer with an ROI will cause an error.

DstIntensityImageBufId

Specifies the identifier of the destination buffer for the resulting gradient intensity image. This parameter must be given an image buffer identifier or M_NULL. Saturation is performed on this buffer.

This image buffer must not have a region of interest (ROI) associated with it. Using an image buffer with an ROI will cause an error.

DstAngleImageBufId

Specifies the identifier of the destination buffer for the resulting gradient angle image. This parameter must be given an image buffer identifier or M_NULL.

This image buffer must not have a region of interest (ROI) associated with it. Using an image buffer with an ROI will cause an error.

Note that this parameter cannot be set to M_NULL if DstIntensityImageBufId is also set to M_NULL, otherwise an error will occur.

KernelId

Specifies the filter to use. This parameter must be set to the value below.

function map For specifying the filter to use
Click to summarizeValue Description
Click to summarize M_SOBEL +

Specifies to use the predefined 3x3 edge detection filters.

The following kernel is convolved with the image to produce GradientX, which is an intermediate image used in the gradient or angle computation. For each pixel, GradientX contains directional derivative values calculated from horizontal (X-direction) intensity changes.

The following kernel is convolved with the image to produce GradientY, which, like GradientX, is an intermediate image used in the gradient or angle computation. For each pixel, GradientY contains directional derivative values calculated from vertical (Y-direction) intensity changes.

(summarize)
Combination values for the values listed in For specifying the filter to use.

You can add one of the following values to the above-mentioned value to specify the overscan settings to use for the operation.

function map For specifying the overscan setting
Click to summarizeCombination value Description
Click to summarize M_OVERSCAN_DISABLE

Specifies to disable overscanning for this operation. You should disable overscanning to accelerate the operation for applications in which the overscan data is not important in the resulting buffer.

(summarize)
Click to summarize M_OVERSCAN_ENABLE

Specifies to enable overscanning for this operation. The overscan uses pixels from the ancestor of the source buffer. If the source buffer is not a child buffer, or if the point falls outside the ancestor buffer, a mirror type overscan is used. A mirror overscan specifies that the overscan pixels will be a mirror copy of the source buffer's border pixels.

This is the default value.

(summarize)
Click to summarize M_OVERSCAN_FAST

Specifies that MIL 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.

(summarize)
ControlFlag

Specifies how to perform the operation.

This parameter can be set to one of the following:

function map For specifying how to perform the operation
Click to summarizeValue Description
Click to summarize M_DEFAULT

Same as M_FAST_EDGE_DETECT.
Click to summarize M_FAST_ANGLE + M_REGULAR_GRADIENT

Specifies a full gradient computation and a fast angle approximation.
Click to summarize M_FAST_EDGE_DETECT

Specifies a fast gradient computation and a fast angle approximation. The gradient is computed as an approximation, using the average of the absolute value of the two directional components (X and Y).

(summarize)
Click to summarize M_REGULAR_ANGLE + M_FAST_GRADIENT

Specifies a fast gradient computation and a full angle computation.
Click to summarize M_REGULAR_EDGE_DETECT

Specifies a full gradient computation and a full angle computation. The gradient is computed as the square root of the sum of the square of each directional component (X and Y). This calculation is slower but more precise.

(summarize)
Threshold

Specifies the threshold value for calculating the gradient angle. For a gradient intensity value lower than the threshold value, the angle is not computed (not considered a significant edge) and the resulting angle for that pixel is undetermined. To perform the full operation, set this parameter to zero or M_NULL.

Note that if MIL determines that calculating the gradient angle of all pixels is faster than excluding some pixels from the computation, the threshold value is simply ignored.

Compilation information
Header Include mil.h.
Library Use mil.lib; milim.lib.
DLL Requires mil.dll; milim.dll.
PROC NONE PROC NONE PROC NONE SOBEL OVERSCAN DISABLE OVERSCAN ENABLE OVERSCAN FAST DEFAULT FAST ANGLE M REGULAR GRADIENT FAST EDGE DETECT REGULAR ANGLE M FAST GRADIENT REGULAR EDGE DETECT