galfar.imaginglib/Source/ImagingColors.pas

{
  $Id$
  Vampyre Imaging Library
  by Marek Mauder 
  http://imaginglib.sourceforge.net

  The contents of this file are used with permission, subject to the Mozilla
  Public License Version 1.1 (the "License"); you may not use this file except
  in compliance with the License. You may obtain a copy of the License at
  http://www.mozilla.org/MPL/MPL-1.1.html

  Software distributed under the License is distributed on an "AS IS" basis,
  WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License for
  the specific language governing rights and limitations under the License.

  Alternatively, the contents of this file may be used under the terms of the
  GNU Lesser General Public License (the  "LGPL License"), in which case the
  provisions of the LGPL License are applicable instead of those above.
  If you wish to allow use of your version of this file only under the terms
  of the LGPL License and not to allow others to use your version of this file
  under the MPL, indicate your decision by deleting  the provisions above and
  replace  them with the notice and other provisions required by the LGPL
  License.  If you do not delete the provisions above, a recipient may use
  your version of this file under either the MPL or the LGPL License.

  For more information about the LGPL: http://www.gnu.org/copyleft/lesser.html
}

{ This unit contains functions for manipulating and converting color values.}
unit ImagingColors;

interface

{$I ImagingOptions.inc}

uses
  SysUtils, ImagingTypes, ImagingUtility;

{ Converts RGB color to YUV.}
procedure RGBToYUV(R, G, B: Byte; var Y, U, V: Byte);
{ Converts YIV to RGB color.}
procedure YUVToRGB(Y, U, V: Byte; var R, G, B: Byte);

{ Converts RGB color to YCbCr as used in JPEG.}
procedure RGBToYCbCr(R, G, B: Byte; var Y, Cb, Cr: Byte);
{ Converts YCbCr as used in JPEG to RGB color.}
procedure YCbCrToRGB(Y, Cb, Cr: Byte; var R, G, B: Byte);
{ Converts RGB color to YCbCr as used in JPEG.}
procedure RGBToYCbCr16(R, G, B: Word; var Y, Cb, Cr: Word);
{ Converts YCbCr as used in JPEG to RGB color.}
procedure YCbCrToRGB16(Y, Cb, Cr: Word; var R, G, B: Word);

{ Converts RGB color to CMY.}
procedure RGBToCMY(R, G, B: Byte; var C, M, Y: Byte);
{ Converts CMY to RGB color.}
procedure CMYToRGB(C, M, Y: Byte; var R, G, B: Byte);

{ Converts RGB color to CMYK.}
procedure RGBToCMYK(R, G, B: Byte; var C, M, Y, K: Byte);
{ Converts CMYK to RGB color.}
procedure CMYKToRGB(C, M, Y, K: Byte; var R, G, B: Byte);

implementation

procedure RGBToYUV(R, G, B: Byte; var Y, U, V: Byte);
begin
  Y := ClampToByte(Round( 0.257 * R + 0.504 * G + 0.098 * B) + 16);
  V := ClampToByte(Round( 0.439 * R - 0.368 * G - 0.071 * B) + 128);
  U := ClampToByte(Round(-0.148 * R - 0.291 * G + 0.439 * B) + 128);
end;

procedure YUVToRGB(Y, U, V: Byte; var R, G, B: Byte);
var
  CY, CU, CV: LongInt;
begin
  CY := Y - 16;
  CU := U - 128;
  CV := V - 128;
  R := ClampToByte(Round(1.164 * CY - 0.002 * CU + 1.596 * CV));
  G := ClampToByte(Round(1.164 * CY - 0.391 * CU - 0.813 * CV));
  B := ClampToByte(Round(1.164 * CY + 2.018 * CU - 0.001 * CV));
end;

procedure RGBToYCbCr(R, G, B: Byte; var Y, Cb, Cr: Byte);
begin
  Y  := ClampToByte(Round( 0.29900 * R + 0.58700 * G + 0.11400 * B));
  Cb := ClampToByte(Round(-0.16874 * R - 0.33126 * G + 0.50000 * B  + 128));
  Cr := ClampToByte(Round( 0.50000 * R - 0.41869 * G - 0.08131 * B  + 128));
end;

procedure YCbCrToRGB(Y, Cb, Cr: Byte; var R, G, B: Byte);
begin
  R := ClampToByte(Round(Y                        + 1.40200 * (Cr - 128)));
  G := ClampToByte(Round(Y - 0.34414 * (Cb - 128) - 0.71414 * (Cr - 128)));
  B := ClampToByte(Round(Y + 1.77200 * (Cb - 128)));
end;

procedure RGBToYCbCr16(R, G, B: Word; var Y, Cb, Cr: Word);
begin
  Y  := ClampToWord(Round( 0.29900 * R + 0.58700 * G + 0.11400 * B));
  Cb := ClampToWord(Round(-0.16874 * R - 0.33126 * G + 0.50000 * B  + 32768));
  Cr := ClampToWord(Round( 0.50000 * R - 0.41869 * G - 0.08131 * B  + 32768));
end;

procedure YCbCrToRGB16(Y, Cb, Cr: Word; var R, G, B: Word);
begin
  R := ClampToWord(Round(Y                          + 1.40200 * (Cr - 32768)));
  G := ClampToWord(Round(Y - 0.34414 * (Cb - 32768) - 0.71414 * (Cr - 32768)));
  B := ClampToWord(Round(Y + 1.77200 * (Cb - 32768)));
end;

procedure RGBToCMY(R, G, B: Byte; var C, M, Y: Byte);
begin
  C := 255 - R;
  M := 255 - G;
  Y := 255 - B;
end;

procedure CMYToRGB(C, M, Y: Byte; var R, G, B: Byte);
begin
  R := 255 - C;
  G := 255 - M;
  B := 255 - Y;
end;

procedure RGBToCMYK(R, G, B: Byte; var C, M, Y, K: Byte);
begin
  RGBToCMY(R, G, B, C, M, Y);
  K := Min(C, Min(M, Y));
  if K > 0 then
  begin
    C := C - K;
    M := M - K;
    Y := Y - K;
  end;
end;

procedure CMYKToRGB(C, M, Y, K: Byte; var R, G, B: Byte);
begin
   if C + K < 255 then R := 255 - (C + K) else R := 0;
   if M + K < 255 then G := 255 - (M + K) else G := 0;
   if Y + K < 255 then B := 255 - (Y + K) else B := 0;
end;

{
  File Notes:

  -- TODOS ----------------------------------------------------
    - nothing now

  -- 0.21 Changes/Bug Fixes -----------------------------------
    - Added some color space conversion functions and LUTs
      (RGB/YUV/YCrCb/CMY/CMYK).

  -- 0.17 Changes/Bug Fixes -----------------------------------
    - unit created (empty!)
}

end.