THotPDF.RegisterSeparationLUT Method

PDF 1.3+ の Separation color space (ISO 32000-1 8.6.6.4) を宣言し、その tint transform として Function Type 0 sampled lookup table (ISO 32000-1 7.10.2) を使用します。spot-ink color curve が non-linear な場合に使用します。PANTONE Hexachrome-style tint ramps、gamma-corrected density curves、press characterisation に合わせた hand-drawn tone curves、full ICC profile machinery を使わない sRGB-to-spot conversion ICC LUTs などです。zero から single full-strength color endpoint への simple linear ramp では、v2.45.0 の RegisterSeparation entry point が引き続き適用されます

function RegisterSeparationLUT(const ColorantName: AnsiString; const AlternateCS: AnsiString; const Samples: array of byte): AnsiString;

AnsiString RegisterSeparationLUT(const AnsiString& ColorantName, const AnsiString& AlternateCS, const unsigned char* Samples, int SamplesCount);

HotPDF internally calls RegisterSampledFunction to build the Function Type 0 stream with /Domain [0 1], /Range covering each alt-CS channel in [0, 1], /Size [S] where S = Length(Samples) / M, /BitsPerSample 8 and /Order 1 (linear interpolation). The function is wired into a fresh [/Separation /ColorantName /AltCS <FuncRef>] colour-space array shared across pages, matching the layout RegisterSeparation produces - downstream SetFillColorSpace + SetFillColor code paths see no API surface change between the two registrar variants.

ColorantName - PDF Name of the ink (e.g. 'PANTONE 185 C', 'CutContour', 'White'). Spaces are escaped to #20 per PDF 1.7 7.3.5 by the existing name-writer path.

AlternateCS - 'DeviceGray' (M = 1), 'DeviceRGB' (M = 3), or 'DeviceCMYK' (M = 4). The sample stream supplies M output bytes per grid point. Any other value raises an exception.

Samples - raw 8-bit sample bytes ordered (c0_0, c1_0, ..., cM-1_0, c0_1, ..., cM-1_S-1) for S grid points. Length(Samples) must be a positive multiple of M; S is inferred as Length(Samples) / M and must be at least 2 so the function has interpolable range. Linear interpolation between grid points is the default (PDF 1.7 /Order 1).

戻り値: auto-generated color-space name (Sep1、Sep2、...) です。Separation entry は v2.45.0 の RegisterSeparation registry と共有されるため、names は 2 つの variants 全体で monotonically increment します。StrictVersionLock が on で active Version が PDF 1.3 未満の場合は empty string を返します (それ以外では document version は 1.3 に auto-bump されます)

Code Example

// Register a 'HeatLUT' Separation over DeviceRGB whose tint -> RGB
// curve is a 256-sample blue -> green -> red heatmap
var
  CSName: AnsiString;
  Samples: array[0..767] of byte;     // 256 * 3 RGB
  I: Integer;
  T: Single;
begin
  HPDF.BeginDoc;
  for I := 0 to 255 do
  begin
    T := I / 255.0;
    if T < 0.5 then
    begin
      Samples[I*3 + 0] := 0;
      Samples[I*3 + 1] := byte(Round(2.0 * T * 255.0));
      Samples[I*3 + 2] := byte(Round((1.0 - 2.0*T) * 255.0));
    end
    else
    begin
      Samples[I*3 + 0] := byte(Round(2.0 * (T - 0.5) * 255.0));
      Samples[I*3 + 1] := byte(Round((1.0 - 2.0*(T - 0.5)) * 255.0));
      Samples[I*3 + 2] := 0;
    end;
  end;
  CSName := HPDF.RegisterSeparationLUT('HeatLUT', 'DeviceRGB', Samples);
  HPDF.CurrentPage.SetFillColorSpace(CSName);
  HPDF.CurrentPage.SetFillColor([0.5]);    // midpoint -> pure green
  HPDF.CurrentPage.Rectangle(100, 100, 40, 40);
  HPDF.CurrentPage.Fill;
  HPDF.EndDoc;
end;