From: "Andrew Rybenkov" <arybenkov@hotmail.com>
To: "Earl F. Glynn" <efg2@efg2.com>
Subject: ColorQuantizationLibrary: little additions
Date: Mon, 18 Nov 2002 12:19:16 +0300

Hi, Earl.

First of all, maybe you would like to know that I have used the unit in that my Imagizer program.
(release with its implementation will be available in a week).

I made the next changes to it, that you may want to add to your original as well:

1) (changed)
--------------------------------------------------------
    PROCEDURE Process24BitDIB;
[...]
    BEGIN
      Scanline := pRGBArray(DIBSection.dsBm.bmBits);
      FOR j := 0 TO DIBSection.dsBmih.biHeight-1 DO
---------------------------------------------------------

      FOR j := 0 TO Abs(DIBSection.dsBmih.biHeight)-1 DO

as biHeight can be negative (for top->bottom) bitmaps. Personally I always set negative height of a bitmap.

2) (added implementation of Process32BitDIB by trivial copying of Process24BitDIB routine):

[declairing new type]
---------------------------------------------------------
  FUNCTION TColorQuantizer.ProcessImage(CONST Handle:  THandle):  BOOLEAN;
    CONST
      MaxPixelCount = 1048576;  // 2^20 = 1MB shouldn't be much of a limit here

    TYPE
      pRGBArray = ^TRGBArray;
      TRGBArray = ARRAY[0..MaxPixelCount-1] OF TRGBTriple;
---------------------------------------------------------
      pARGBArray = ^TARGBArray;
      TARGBArray = ARRAY[0..MaxPixelCount-1] OF TRGBQuad;

and further

    PROCEDURE Process32BitDIB;
      VAR
        i       :  INTEGER;
        j       :  INTEGER;
        ScanLine:  pARGBArray;
    BEGIN
      Scanline := pARGBArray(DIBSection.dsBm.bmBits);
      FOR j := 0 TO Abs(DIBSection.dsBmih.biHeight)-1 DO
      BEGIN

        FOR i := 0 TO DIBSection.dsBmih.biWidth-1 DO
        BEGIN
          WITH Scanline[i] DO
            AddColor(FTree, rgbRed, rgbGreen, rgbBlue,
                     FColorBits, 0, FLeafCount, FReducibleNodes);

          WHILE FLeafCount > FMaxColors DO
            ReduceTree(FColorbits, FLeafCount, FReducibleNodes)

        END;

        ScanLine := pARGBArray(INTEGER(Scanline) + DIBSection.dsBm.bmWidthBytes);
      END
    END {Process32BitDIB};


Some time later I am going to optimize slightly the unit for speed.
If you have interest in it, please, let me know.


Thanks for great site, and
best wishes,
Andrew Rybenkov.