Color Drop

Hi, I'm trying to implement a method (using C++ or Delphi) that does something similar to scanner's (Red,Green or blue) "Color Drop" function.

After I drop certain colors (something like all except black) from the image I'll try to OCR it.

Which is the proper function for this purpose? I'm working on L_RemapBitmapHue().

Example images are attached.

The best way to do this would be to select a region based on either a single color or a color range.  To do this:

1.
you can use the L_SetBitmapRgnColor, L_SetBitmapRgnColorRGBRange, or L_SetBitmapRgnColorHSVRange function.  For the combine mode, you would want to use L_RGN_SETNOT so that you select everything BUT the color you selected (let's say you only selected black). 

2.
Then you would use L_FillBitmap to fill the region with white. 

3.
Finally, you would use L_FreeBitmapRgn to delete the regoin from the bitmap before doing anything else.

Thank you, it is working like a charm..

For anybody who wants such a function in Delphi. I used L_RemapBitmapHue() function to convert any pixel that has a less light value than 170 to pure black. Than removed any color but black in the following code :

procedure TMainForm.Button11Click(Sender: TObject);
var
i : integer;
uMaskTable : array [0..255] of L_UINT;
uValTable : array [0..255] of L_UINT;
uLUTLen : L_INT;
nRet : L_INT;
rgbLower : COLORREF;
rgbHigher : COLORREF;
crRgnColor : COLORREF;
fSmooth : SMOOTH;
fDotRemove : DOTREMOVE;
br : BORDERREMOVE;
begin
uLUTLen := 256;
for i:=0 to uLUTLen-1 do
begin
uMaskTable[i] := 1;
if i>170 then
uValTable[i]:=i
else
uValTable[i]:=0;
end;

nRet := L_RemapBitmapHue(@Bitmap1, @uMaskTable, nil, nil, @uValTable, uLUTLen);
if nRet=SUCCESS then begin
rgbLower := RGB(0,0,0);
rgbHigher := RGB(0,0,0);
nRet := L_SetBitmapRgnColorRGBRange(@Bitmap1,rgbLower,rgbHigher,L_RGN_SETNOT);
if (nRet=SUCCESS) then begin
if (L_BitmapHasRgn(@Bitmap1)) then begin
crRgnColor := RGB(255,255,255);
nRet := L_FillBitmap(@Bitmap1, crRgnColor);
if (nRet=SUCCESS) then begin
nRet := L_ColorResBitmap(@Bitmap1, @Bitmap1, sizeof(BITMAPHANDLE)
, 1
, CRF_NODITHERING or CRF_FIXEDPALETTE or CRF_BYTEORDERBGR
, nil, 0, 0, nil, nil);
if nret=Success then begin
HandlePalette ( false );
invalidate;
end;
end;
L_FreeBitmapRgn(@Bitmap1);
end;
end;
end;
end;

Am trying to implement the routine you have provided using Visual Basic, I am unable to call/reference the DLL's that include the functions used above.

How do I reference and access the functions/subroutines used in the above routine of dropping color Visual Basic 6?

Thanks

He is using the CDLL interface, so you need to declare the functions so you can use them in VB6.  This is done the same way that you would any other Windows API function call.  Documentation of the functions and structures can be found in the CDLL (or API if you are using something v15 and older) help files.