🚀 go-pugleaf

Hello,

I have to lighter or darker  a pixel depending of a coeff.

my problem is to do it correctly I have to convert the RGB value to HSV,
aplly the coff to the V and then back to RGB.

the code that I have in object pascal is pretty long when doing it on all
pixels of a bitmap.

Do someone has a routine in assembly for fast conversion of RGB <-> HSV?

thanks

Armindo


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//
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procedure RGBToHSV (const R,G,B: single; var H,S,V: single);
var Delta, Min: single;
begin
  Min := MinValue( [R, G, B] );    // USES Math
  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 H := 60.0 * (G - B) / Delta                // between
yellow and magenta [degrees]
    else
      if G = V then H := 120.0 + 60.0 * (B - R) / Delta      // between cyan
and yellow
      else
        if B = V then H := 240.0 + 60.0 * (R - G) / Delta;   // between
magenta and cyan
    if H < 0.0 then H := H + 360.0
  end
end ;

//
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//
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procedure HSVtoRGB (const H,S,V: single; var R,G,B: single);
var f, p, q, t, hTemp : single;                             // since H is
CONST parameter
    i : INTEGER;
begin
  if S = 0.0 then begin                                     // color is on
black-and-white center line
    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 then hTemp := 0.0                          // 360 degrees
same as 0 degrees
    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 ;

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