GetImagePointer

Description

Returns the pointer to the pixel at the specified coordinates of the current frame.


Syntax

[VB]
Value=objActiveGige.GetImagePointer( X, Y )

[C/C++]
HRESULT GetImagePointer( short X, short Y, VARIANT* pValue );


Data Types [VB]

X: Integer
Y: Integer
Return value: Variant (pointer)


Parameters [C/C++]

X [in]

The x-coordinate of the pixel

Y [in]

The y-coordinate of the pixel

pValue [out,retval]

Pointer to the variant containing the pointer to the specified memory location

Return Values

S_OK

Success

E_FAIL

Failure.

E_INVALIDARG

Invalid input arguments.

Example

This C++ example grabs a frame, retrieves a pointer to the 32th line in the frame memory and copies the pixels values into a byte array . A wrapper class CActiveGige is used to access the ActiveGige control:

BYTE line[4096];
int iWidth=m_ActiveGige.GetSizeX();
int iHeight=m_ActiveGige.GetSizeY();
m_ActiveGige.Grab()
VARIANT v=m_ActiveGige.GetImagePointer(0,iHeight-1-32);
memcpy(&line,v.pcVal,iWidth);
This C# example uses the FrameAcquired event to retrieve a pointer to the 32th line in the frame memory and change pixel values in the line to zeros:

private void axActiveGige1_FrameAcquired(object sender, AxACTIVEGIGELib._IActiveGigeEvents_FrameAcquiredEvent e)
{
int sx=axActiveGige1.SizeX;
int sy=axActiveGige1.SizeY;
object obj=axActiveGige1.GetImagePointer(0, sy-1-32);
int a = (int)obj;
byte* ptr= (byte*)a;
for (int x=0; x<sx; x++, ptr++)
 *ptr=0;
}

Remarks

The GetImagePointer method provides the most efficient way to quickly access the internal image buffer in pointer-aware programming languages. Unlike GetImageData, this method doesn't modify original pixel values of high-bit depth images. The number of bytes in each line of the image buffer depends on the format and horizontal size of the video as specified in the following table:

Camera Pixel Format	Output Format	Line width in bytes
Mono8	8-bit monochrome	SizeX
Mono10, Mono12, Mono16	16-bit monochrome	SizeX * 2
YUV411, YUV422, YUV444, RGB8, BGR8, Bayer8	24-bit RGB	SizeX * 3
RGB10, RGB12, RGB16, BGR10, BGR12, Bayer10, Bayer12, Bayer16	48-bit RGB	SizeX * 6

Images in ActiveGige are stored bottom up, therefore the zero vertical coordinate corresponds to the bottom line of the image.

The values of the x and y coordinates must not exceed the width and height of the video frame, or the error will occur.

Note that if images are transmitted by a linescan camera, the number of lines in each image can vary and be less than the vertical size of the image frame defined by the SizeY property. See GetHeight for more details.