Multiple regions of interest (ROIs) on an image

If you use LEADTOOLS Document Imaging, which has Annotations support,
you can define an annotation object (such as a freehand object or a
rectangle object), then obtain a region based on the annotation
object's location. This is done using the L_AnnGetRgnHandle API function (which can be used with VCL).

Then, you can use the VCL SetRgnHandle method to set the region into
the control. Finally, use any image processing function from those that apply to the region only.


If you need multiple regions together, you can repeat the process of
calling L_AnnGetRgnHandle, and use the L_RGN_OR flag with the SetRgnHandle method to create a composite region.

Amin Dodin

LEADTOOLS Technical Support

Thanks Amin,

I tried the L_AnnGetRgnHandle but could not get it to work (access violations and stuff). I am not sure if the type definitions are right and if the function call is right  as well.

Here's what I tried to do:

type pRGNXFORM = ^RGNXFORM;
type pL_HRGN = ^L_HRGN;
function L_AnnGetRgnHandle(hObject: HANNOBJECT; pXForm: pRGNXFORM; phRgn: pL_HRGN): L_INT; stdcall; external 'ltann14e.dll';

procedure TForm1.Lead1AnnDrawn(hObject: L_HANDLE);
var
  rgn: pL_HRGN;
begin
  Lead1.AnnTool := 0;

  L_AnnGetRgnHandle(hObject, ni, rgn);

  Lead1.SetRgnHandle(rgn^, 0, 0, L_RGN_SET);
  Lead1.Emboss(EMBOSS_SE, 500);
end;

 

Please shed some light on the matter!

Thanks!

This is a sample test procedure that creates a region based on an annotation object.

You can use L_AnnGetRgnHandle and other API functions by adding leadunt
to the Uses section. You will also need leadtyp and leaddef for data types and constant values.

procedure TForm1.TestAnnAPI();
var
  hEllipseObject : L_HANDLE;
  Rgn : L_HRGN;
Begin
  // Create an ellipse object and define its location
  hEllipseObject := LEADAnn1.AnnCreate(ANNOBJECT_ELLIPSE, True, True);
  LEADAnn1.AnnDefine(hEllipseObject, 80, 60, ANNDEFINE_BEGINSET);
  LEADAnn1.AnnDefine(hEllipseObject, 180, 260, ANNDEFINE_END);
  // Get a region based on the object
  L_AnnGetRgnHandle(hEllipseObject, nil, @Rgn);
  // No longer need the Ann object
  LEADAnn1.AnnDestroy(hEllipseObject, 0);
  // Set the region into the control
  LEADAnn1.SetRgnHandle(Rgn, 0, 0, L_RGN_SET);
  // No longer need the handle. MUST free it
  LEADAnn1.DeleteRgnHandle(Rgn);
  // Test region is working
  LEADAnn1.Emboss(EMBOSS_SE, 500);
End;

Amin Dodin
LEADTOOLS Technical Support