{
  $Id: ImagingColors.pas 173 2009-09-04 17:05:52Z galfar $
  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 CMY.}
procedure RGBToCMY16(R, G, B: Word; var C, M, Y: Word);
{ Converts CMY to RGB color.}
procedure CMYToRGB16(C, M, Y: Word; var R, G, B: Word);

{ 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);
{ Converts RGB color to CMYK.}
procedure RGBToCMYK16(R, G, B: Word; var C, M, Y, K: Word);
{ Converts CMYK to RGB color.}
procedure CMYKToRGB16(C, M, Y, K: Word; var R, G, B: Word);

{ Converts RGB color to YCoCg.}
procedure RGBToYCoCg(R, G, B: Byte; var Y, Co, Cg: Byte);
{ Converts YCoCg to RGB color.}
procedure YCoCgToRGB(Y, Co, Cg: 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 RGBToCMY16(R, G, B: Word; var C, M, Y: Word);
begin
  C := 65535 - R;
  M := 65535 - G;
  Y := 65535 - B;
end;

procedure CMYToRGB16(C, M, Y: Word; var R, G, B: Word);
begin
  R := 65535 - C;
  G := 65535 - M;
  B := 65535 - 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 = 255 then
  begin
    C := 0;
    M := 0;
    Y := 0;
  end
  else
  begin
    C := ClampToByte(Round((C - K) / (255 - K) * 255));
    M := ClampToByte(Round((M - K) / (255 - K) * 255));
    Y := ClampToByte(Round((Y - K) / (255 - K) * 255));
  end;
end;

procedure CMYKToRGB(C, M, Y, K: Byte; var R, G, B: Byte);
begin
   R := (255 - (C - MulDiv(C, K, 255) + K));
   G := (255 - (M - MulDiv(M, K, 255) + K));
   B := (255 - (Y - MulDiv(Y, K, 255) + K));
end;

procedure RGBToCMYK16(R, G, B: Word; var C, M, Y, K: Word);
begin
  RGBToCMY16(R, G, B, C, M, Y);
  K := Min(C, Min(M, Y));
  if K = 65535 then
  begin
    C := 0;
    M := 0;
    Y := 0;
  end
  else
  begin
    C := ClampToWord(Round((C - K) / (65535 - K) * 65535));
    M := ClampToWord(Round((M - K) / (65535 - K) * 65535));
    Y := ClampToWord(Round((Y - K) / (65535 - K) * 65535));
  end;
end;

procedure CMYKToRGB16(C, M, Y, K: Word; var R, G, B: Word);
begin
  R := 65535 - (C - MulDiv(C, K, 65535) + K);
  G := 65535 - (M - MulDiv(M, K, 65535) + K);
  B := 65535 - (Y - MulDiv(Y, K, 65535) + K);
end;

procedure RGBToYCoCg(R, G, B: Byte; var Y, Co, Cg: Byte);
begin
  // C and Delphi's SHR behaviour differs for negative numbers, use div instead.
  Y  := ClampToByte(( R +     G shl 1 + B       + 2) div 4);
  Co := ClampToByte(( R shl 1         - B shl 1 + 2) div 4 + 128);
  Cg := ClampToByte((-R +     G shl 1 - B       + 2) div 4 + 128);
end;

procedure YCoCgToRGB(Y, Co, Cg: Byte; var R, G, B: Byte);
var
  CoInt, CgInt: Integer;
begin
  CoInt := Co - 128;
  CgInt := Cg - 128;
  R := ClampToByte(Y + CoInt - CgInt);
  G := ClampToByte(Y + CgInt);
  B := ClampToByte(Y - CoInt - CgInt);
end;

{
  File Notes:

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

  -- 0.26.3 Changes/Bug Fixes ---------------------------------
    - Added RGB<>YCoCg conversion functions.
    - Fixed RGB>>CMYK conversions.

  -- 0.23 Changes/Bug Fixes -----------------------------------
    - Added RGB<>CMY(K) converion functions for 16 bit channels
      (needed by PSD loading code).

  -- 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.
