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// Real (as in "Float") Color Library
//
// efg, September 1998
// September 2001, HLStoRGB error corrected.
UNIT RealColorLibrary;
INTERFACE
USES
Windows, // TRGBQuad
Graphics, // TBitmap
ImageProcessingPrimitives; // TReal, pRGBQuadArray
TYPE
TRealToRGBConversion = PROCEDURE (CONST x: TReal; VAR R,G,B: BYTE);
TRealColorMatrix = // pf32bit Bitmap, or matrix of single float values
CLASS(TBitmap)
PRIVATE
FUNCTION GetReal(i,j: Integer): TReal;
PROCEDURE SetReal(i,j: Integer; value: TReal);
PUBLIC
CONSTRUCTOR Create; Override;
PROCEDURE ConvertRealMatrixToRGBImage(ConversionFunction: TRealToRGBConversion);
PROPERTY Element[i,j: Integer]: TReal READ GetReal Write SetReal; DEFAULT;
END;
// Color Conversions
// HLS
PROCEDURE HLStoRGB(CONST H,L,S: TReal; VAR R,G,B: TReal);
PROCEDURE RGBToHLS(CONST R,G,B: TReal; VAR H,L,S: TReal);
// HSV
PROCEDURE HSVtoRGB(CONST H,S,V: TReal; VAR R,G,B: TReal);
PROCEDURE RGBToHSV(CONST R,G,B: TReal; VAR H,S,V: TReal);
// CMY
PROCEDURE CMYtoRGB(CONST C,M,Y: TReal; VAR R,G,B: TReal);
PROCEDURE RGBToCMY(CONST R,G,B: TReal; VAR C,M,Y: TReal);
// CMYK
PROCEDURE CMYKtoRGB(CONST C,M,Y,K: TReal; VAR R,G,B : TReal);
PROCEDURE RGBToCMYK(CONST R,G,B : TReal; VAR C,M,Y,K: TReal);
// Color Matrices: All Bitmap parameters are pf24bit bitmaps
PROCEDURE BitmapToRGBMatrices(CONST Bitmap: TBitmap;
VAR Red,Green,Blue: TRealColorMatrix);
FUNCTION RGBMatricesToBitmap(CONST Red,Green,Blue: TRealColorMatrix): TBitmap;
PROCEDURE RGBMatricesToHSVMatrices(CONST Red,Green,Blue: TRealColorMatrix;
VAR Hue,Saturation,Value: TRealColorMatrix);
PROCEDURE HSVMatricesToRGBMatrices(CONST Hue,Saturation,Value: TRealColorMatrix;
VAR Red,Green,Blue: TRealColorMatrix);
IMPLEMENTATION
USES
Math, // MaxValue
IEEE754, // NAN (not a number)
SysUtils; // Exception
TYPE
EColorError = CLASS(Exception);
// == TColorMatrix ====================================================
//
CONSTRUCTOR TRealColorMatrix.Create;
BEGIN
ASSERT (SizeOf(TRGBQuad) = SizeOf(TReal)); // to be sure
Inherited Create;
PixelFormat := pf32bit; // Each "pixel" is a "single"
END {Create};
PROCEDURE TRealColorMatrix.ConvertRealMatrixToRGBImage(ConversionFunction: TRealToRGBConversion);
VAR
FloatRow: pSingleArray;
i : INTEGER;
j : INTEGER;
PixelRow: pRGBQuadArray;
R,G,B : BYTE;
BEGIN
FOR j := 0 TO Height-1 DO
BEGIN
PixelRow := Scanline[j];
FloatRow := Scanline[j];
FOR i := 0 TO Width-1 DO
BEGIN
ConversionFunction(FloatRow
, R,G,B);
WITH PixelRow DO
BEGIN
rgbRed := R;
rgbGreen := G;
rgbBlue := B;
rgbReserved := 0
END
END
END
END {ConvertSingleToRGB};
FUNCTION TRealColorMatrix.GetReal(i,j: Integer): TReal;
BEGIN
RESULT := pSingleArray(Scanline[j])
END {GetSingle};
PROCEDURE TRealColorMatrix.SetReal(i,j: Integer; value: TReal);
BEGIN
pSingleArray(Scanline[j]) := value
END {SetSingle};
// == HLS / RGB =======================================================
//
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 596.
PROCEDURE HLStoRGB(CONST H,L,S: TReal; VAR R,G,B: TReal);
VAR
m1: TReal;
m2: TReal;
FUNCTION Value(CONST n1,n2: TReal; hue: TReal): TReal;
BEGIN
IF hue > 360.0
THEN hue := hue - 360.0
ELSE
IF hue < 0.0
THEN hue := hue + 360.0;
IF hue < 60.0
THEN RESULT := n1 + (n2 - n1)*hue / 60.0
ELSE
IF hue < 180
THEN RESULT := n2
ELSE
IF hue < 240.0
THEN RESULT := n1 + (n2-n1)*(240.0 - hue) / 60.0
ELSE RESULT := n1
END {Value};
BEGIN
// There is an error in Computer Graphics Principles and Practice,
// Foley, et al, 1996, pp. 592-596. The formula uses a lower case
// "el", "l", and defines in C:
//
// m2 = (l < 0.5) ? (l * (l+s))
l+s-l*s)
//
// This is a perfect example of why "l" (a lower case "el") should
// NEVER be used as a variable name, and why a programming convention --
// to use lower case letters in variable names -- should not override
// the problem definition, which defines the color space using an "L".
// The 1982 version of the book, in Pascal, shows the correct formula
// (but alas, also used a lower case "l"):
//
// if l <= 0.5
// then m2 := l*(1+s) // NOTE the one, in "1+s", here
// else m2 := l + s - l*s&nbsp;
//
// [Thanks to Gary Freestone, IBM Global Services Australia, for
// bringing this to my attention. efg, Sept. 2001]
IF L <= 0.5
THEN m2 := L * (1 + S)
ELSE m2 := L + S - L*S;
m1 := 2.0 * L - m2;
IF S = 0.0
THEN BEGIN // achromatic -- no hue
IF IsNAN(H)
THEN BEGIN
R := L;
G := L;
B := L
END
ELSE RAISE EColorError.Create('HLStoRGB: S = 0 and H has a value');
END
ELSE BEGIN
// Chromatic case -- there is a hue
R := Value(m1, m2, H + 120.0);
G := Value(m1, m2, H);
B := Value(m1, m2, H - 120.0)
END
END {HLStoRGB};
// H = 0 to 360 (corresponding to 0..360 degrees around hexcone)
// L = 0.0 (shade of gray) to 1.0 (pure color)
// S = 0.0 (black) to 1.0 {white)
//
// R, G, B each in [0,1]
//
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 595.
PROCEDURE RGBToHLS (CONST R,G,B: TReal; VAR H,L,S: TReal);
VAR
Delta: TReal;
Max : TReal;
Min : TReal;
BEGIN
Max := MaxValue( [R, G, B] );
Min := MinValue( [R, G, B] );
L := (Max + Min) / 2.0; // Lightness
IF Max = Min // Achromatic case since r = g = b
THEN BEGIN
S := 0.0;
H := NAN; // Undefined
END
ELSE BEGIN
Delta := Max - Min;
IF L <= 0.5
THEN S := Delta / (Max + Min)
ELSE S := Delta / (2.0 - (Max + Min));
IF R = Max
THEN // degrees between yellow and magenta
H := (60.0*(G - B)) / Delta
ELSE
IF G = Max
THEN // degrees between cyan and yellow
H := 120.0 + (60.0*(B - R)) / Delta
ELSE
IF B = Max
THEN // degrees between magenta and cyan
H := 240.0 + (60.0*(R - G)) / Delta;
IF H < 0
THEN H := H + 360.0; // Keep in interval [0, 360)
END
END {RGBtoHLS};
// == HSV / RGB =======================================================
//
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 593.
//
// H = 0.0 to 360.0 (corresponding to 0..360 degrees around hexcone)
// NaN (undefined) for S = 0
// S = 0.0 (shade of gray) to 1.0 (pure color)
// V = 0.0 (black) to 1.0 (white)
PROCEDURE HSVtoRGB (CONST H,S,V: TReal; VAR R,G,B: TReal);
VAR
f : TReal;
i : INTEGER;
hTemp: TReal; // since H is CONST parameter
p,q,t: TReal;
BEGIN
IF S = 0.0 // color is on black-and-white center line
THEN BEGIN
IF IsNaN(H)
THEN BEGIN
R := V; // achromatic: shades of gray
G := V;
B := V
END
ELSE RAISE EColorError.Create('HSVtoRGB: S = 0 and H has a value');
END
ELSE BEGIN // chromatic color
IF H = 360.0 // 360 degrees same as 0 degrees
THEN hTemp := 0.0
ELSE hTemp := H;
hTemp := hTemp / 60; // h is now IN [0,6)
i := TRUNC(hTemp); // largest integer <= h
f := hTemp - i; // fractional part of h
p := V * (1.0 - S);
q := V * (1.0 - (S * f));
t := V * (1.0 - (S * (1.0 - f)));
CASE i OF
0: BEGIN R := V; G := t; B := p END;
1: BEGIN R := q; G := V; B := p END;
2: BEGIN R := p; G := V; B := t END;
3: BEGIN R := p; G := q; B := V END;
4: BEGIN R := t; G := p; B := V END;
5: BEGIN R := V; G := p; B := q END
END
END
END {HSVtoRGB};
// RGB, each 0 to 255, to HSV.
// H = 0.0 to 360.0 (corresponding to 0..360.0 degrees around hexcone)
// S = 0.0 (shade of gray) to 1.0 (pure color)
// V = 0.0 (black) to 1.0 {white)
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 592. Floating point fractions, 0..1, replaced with
// integer values, 0..255.
PROCEDURE RGBToHSV (CONST R,G,B: TReal; VAR H,S,V: TReal);
VAR
Delta: TReal;
Min : TReal;
BEGIN
Min := MinValue( [R, G, B] );
V := MaxValue( [R, G, B] );
Delta := V - Min;
// Calculate saturation: saturation is 0 if r, g and b are all 0
IF V = 0.0
THEN S := 0
ELSE S := Delta / V;
IF S = 0.0
THEN H := NAN // Achromatic: When s = 0, h is undefined
ELSE BEGIN // Chromatic
IF R = V
THEN // between yellow and magenta [degrees]
H := 60.0 * (G - B) / Delta
ELSE
IF G = V
THEN // between cyan and yellow
H := 120.0 + 60.0 * (B - R) / Delta
ELSE
IF B = V
THEN // between magenta and cyan
H := 240.0 + 60.0 * (R - G) / Delta;
IF H < 0.0
THEN H := H + 360.0
END
END {RGBtoHSV};
// == CMY / RGB =======================================================
//
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 588
// R, G, B, C, M, Y each IN [0.0 .. 1.0]
PROCEDURE CMYtoRGB(CONST C,M,Y: TReal; VAR R,G,B: TReal);
BEGIN
R := 1.0 - C;
G := 1.0 - M;
B := 1.0 - Y
END {CMYtoRGB};
// R, G, B, C, M, Y each IN [0.0 .. 1.0]
PROCEDURE RGBtoCMY(CONST R,G,B: TReal; VAR C,M,Y: TReal);
BEGIN
C := 1.0 - R;
M := 1.0 - G;
Y := 1.0 - B
END {RGBtoCMY};
// == CMYK / RGB ======================================================
//
// Based on C Code in "Computer Graphics -- Principles and Practice,"
// Foley et al, 1996, p. 589
// R, G, B, C, M, Y, K each IN [0.0 .. 1.0]
PROCEDURE CMYKtoRGB(CONST C,M,Y,K: TReal; VAR R,G,B: TReal);
BEGIN
R := 1.0 - (C + K);
G := 1.0 - (M + K);
B := 1.0 - (Y + K)
END {CMYtoRGB};
// R, G, B, C, M, Y each IN [0.0 .. 1.0]
PROCEDURE RGBToCMYK(CONST R,G,B: TReal; VAR C,M,Y,K: TReal);
BEGIN
RGBtoCMY(R,G,B, C,M,Y);
K := MinValue([C, M, Y]);
C := C - K;
M := M - K;
Y := Y - K
END {RGBtoCMYK};
// == Color Matrices =================================================
//
PROCEDURE BitmapToRGBMatrices(CONST Bitmap: TBitmap;
VAR Red,Green,Blue: TRealColorMatrix);
VAR
i,j: INTEGER;
row: pRGBTripleArray;
BEGIN
ASSERT (Bitmap.PixelFormat = pf24bit);
Red := TRealColorMatrix.Create;
Red.Width := Bitmap.Width;
Red.Height := Bitmap.Height;
Green := TRealColorMatrix.Create;
Green.Width := Bitmap.Width;
Green.Height := Bitmap.Height;
Blue := TRealColorMatrix.Create;
Blue.Width := Bitmap.Width;
Blue.Height := Bitmap.Height;
FOR j := 0 TO Bitmap.Height-1 DO
BEGIN
row := Bitmap.Scanline[j];
FOR i := 0 TO Bitmap.Width-1 DO
BEGIN
Red[i,j] := row.rgbtRed / 255; // 0.0 to 1.0
Green[i,j] := row.rgbtGreen / 255;
Blue[i,j] := row.rgbtBlue / 255;
END
END
END {BitmapToRGBMatrices};
FUNCTION RGBMatricesToBitmap(CONST Red,Green,Blue: TRealColorMatrix): TBitmap;
VAR
i,j: INTEGER;
row: pRGBTripleArray;
BEGIN
ASSERT( (Red.Width = Green.Width) AND
(Red.Width = Blue.Width) AND
(Red.Height = Green.Height) AND
(Red.Height = Blue.Height) );
RESULT := TBitmap.Create;
RESULT.Width := Red.Width;
RESULT.Height := Red.Height;
RESULT.PixelFormat := pf24bit;
FOR j := 0 TO Red.Height-1 DO
BEGIN
row := RESULT.Scanline[j];
FOR i := 0 TO Red.Width-1 DO
BEGIN
WITH row DO
BEGIN
rgbtRed := TRUNC(Red[i,j] * 255 + 0.5);
rgbtGreen := TRUNC(Green[i,j] * 255 + 0.5);
rgbtBlue := TRUNC(Blue[i,j] * 255 + 0.5);
END
END
END
END {RGBMatricesToBitmap};
PROCEDURE RGBMatricesToHSVMatrices(CONST Red,Green,Blue: TRealColorMatrix;
VAR Hue,Saturation,Value: TRealColorMatrix);
VAR
i,j : INTEGER;
H,S,V: TReal;
BEGIN
ASSERT( (Red.Width = Green.Width) AND
(Red.Width = Blue.Width) AND
(Red.Height = Green.Height) AND
(Red.Height = Blue.Height) AND
(Hue.Width = Saturation.Width) AND
(Hue.Width = Value.Width) AND
(Hue.Height = Saturation.Height) AND
(Hue.Height = Value.Height) );
FOR j := 0 TO Red.Height-1 DO
BEGIN
FOR i := 0 TO Red.Width-1 DO
BEGIN
RGBToHSV(Red[i,j], Green[i,j], Blue[i,j], H, S, V);
Hue[i,j] := H;
Saturation[i,j] := S;
Value[i,j] := V
END
END
END {RGBMatricesToHSVMatrices};
PROCEDURE HSVMatricesToRGBMatrices(CONST Hue,Saturation,Value: TRealColorMatrix;
VAR Red,Green,Blue: TRealColorMatrix);
VAR
i,j : INTEGER;
R,G,B: TReal;
BEGIN
ASSERT( (Red.Width = Green.Width) AND
(Red.Width = Blue.Width) AND
(Red.Height = Green.Height) AND
(Red.Height = Blue.Height) AND
(Hue.Width = Saturation.Width) AND
(Hue.Width = Value.Width) AND
(Hue.Height = Saturation.Height) AND
(Hue.Height = Value.Height) );
FOR j := 0 TO Red.Height-1 DO
BEGIN
FOR i := 0 TO Red.Width-1 DO
BEGIN
HSVToRGB(Hue[i,j],
Saturation[i,j],
Value[i,j],
R, G, B);
Red[i,j] := R;
Green[i,j] := G;
Blue[i,j] := B
END
END
END {HSVMatriceesToRGBMatrices};
END.