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Common Vision Blox offers fast and flexible access to image data via two technologies:

 

VPAT - Virtual Pixel Access Table

Scan Functions

 

VPAT - Virtual Pixel Access Table

 

The VPA table allows read and write access to all pixels using the base address, the tables for the offset of the lines and the table for the pixel offset within a line.

 

•if image data is linear then the GetLinearAccess function gives the fastest access

•if not linear then the GetImageVPA function can be used

•fast by pointer access

•compatible to most existing algorithms

•reducable to a line pointer (y-Table)

•reducable to straight pointer to first pixel (BaseAddress)

 

 

GetLinearAccess

This function uses the AnalysexVPAT functions to verify if the image can support direct linear access to the data.

If the function returns TRUE, it is possible to access the image data via a pointer.

The function allows existing algorithms to be ported CVB images quickly and efficiently.

 

Note: This function is not supported in Visual Basic due to the programming language not supporting pointers.

 

GetLinearAccess is the preferred way to access the image data.

If not available you can use VPAT Access via the GetImageVPA function.

 

Function description and code examples can be found here :

%CVB%Tutorial\Image Manager\VC\VCAnalyseVPAT

 

GetImageVPA

This function allows access to the virtual pixel access table (VPA).

The VPA tables allow read and write access to all pixels using the base address, the tables for the offset of the lines, and the table for the pixel offset within a line.

 

Function description and code examples can be found here

%CVB%Tutorial\Image Manager\VC\VCVPAT

 

 

Scan Functions

 

Using Scan Functions the scan direction and search direction can be manipulated.

For example by controlling the vectors  the scan direction can be changed.

The first scan line is always from P0 to P1, and the scan direction is always from P0 to P2.

 

•fast access with DLL-functions

•convenient pixel access via "Callback-Functions"

•fully supports rotated CVB-Areas

•support of the CVB coordinate system

•optionally restricted to a selectable image region (AOI)

•parallel scan on one or two images

•available in OCX for compatibility reasons to VB users, but they are slow

 

 

ScanImageUnary (DLL)

This dll-function allows access to all planes of the image taking Area and Density into consideration.

 

ScanPlaneUnary (DLL)

This dll-function allows access to a plane of an image taking area and density into consideration.

Function description within a tutorial can be found here:

%CVB%Tutorial\Image Manager\VC\VCAccess

 

ScanImageBinary (DLL)

This dll-function allows simultaneous access to the two different images taking Area and Density into consideration.

This could be used for example to link two images via a lookup table.

 

ScanPlaneBinary (DLL)

This dll-function allows simultaneous access to the two different specified planes of two images taking Area and Density into consideration.

This could be used for example to link two images via a lookup table.

 

ScanImage (OCX)

This functions gives Visual Basic users access to the ScanImage functionality.

 

ScanPlane (OCX)

This functions gives Visual Basic users access to the ScanPlane functionality.