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Cropping an image is a simple task for Gdiplus.

One of the ways that this can be done is using the Gdi+ function GdipCloneBitmapAreaI , that unfortunately was not included in _gdiplus.vcx, but can be easily accessed. 

Original Image 

Top Left  

                                Center 

                                                   Bottom Right 

Run the code below, selecting any image, and you will see the image cropped in three ways: the top-left part of the image, the bottom-right part, and the center.

IF EMPTY(lcSource)
   RETURN
ENDIF
* Load Image to Gdiplus
LOCAL loImage AS GpImage OF HOME() + ffc/_gdiplus.vcx
loImage = NEWOBJECT("GpImage",HOME()+"ffc/_gdiplus.vcx")
loImage.CreateFromFile(lcSource)
lnWidth = loImage.ImageWidth
lnHeight = loImage.ImageHeight

PROCEDURE Crop(toImage, x, Y, tnWidth, tnHeight, tnPixelFormat)
   IF VARTYPE(tnPixelFormat) = "L"
      tnPixelFormat = toImage.PixelFormat
   ENDIF
   * GpStatus WINGDIPAPI GdipCloneBitmapAreaI
   * (INT x, INT y, INT width, INT height, PixelFormat format,
   * GpBitmap *srcBitmap, GpBitmap **dstBitmap)
   DECLARE LONG GdipCloneBitmapAreaI IN GDIPLUS.dll ;
      LONG x, LONG Y, LONG nWidth, LONG nHeight, ;
      LONG PixelFormat, LONG srcBitmap, LONG @dstBitmap
   LOCAL lnNewBitmap
   lnNewBitmap = 0
   = GdipCloneBitmapAreaI(x, Y, tnWidth, tnHeight, ;
      tnPixelFormat, toImage.GetHandle(), @lnNewBitmap)
   LOCAL loNewImage
   loNewImage = NEWOBJECT("GpBitmap",HOME()+"ffc/_gdiplus.vcx")
   loNewImage.SetHandle(lnNewBitmap)
   RETURN loNewImage
ENDPROC

To achieve this, I created a small procedure, "crop", that receives the following parameters retrieved from MSDN :

toImage - Image or Bitmap object

X  - Integer that specifies the x-coordinate of the upper-left corner of the rectangle that specifies the portion of this bitmap to copy.

Y  - Integer that specifies the y-coordinate of the upper-left corner of the rectangle that specifies the portion of this bitmap to copy.

Width - Integer that specifies the width of the rectangle that specifies the portion of this bitmap to copy.

Height - Integer that specifies the height of the rectangle that specifies the portion of this image to copy.

Format - optional, Integer that specifies the pixel format of the new bitmap. The PixelFormat data type and constants that represent various pixel formats are defined in Gdiplus.h. For more information about pixel format constants, see Image Pixel Format Constants.

Return - This method returns a pointer to the new Bitmap object containing the cropped image.