THotPDF.RegisterSeparationLUT Method

يعلن Separation colour space في PDF 1.3+ (ISO 32000-1 8.6.6.4) يكون tint transform فيه Function Type 0 sampled lookup table (ISO 32000-1 7.10.2). استخدمه عندما يكون منحنى spot-ink color غير خطي، مثل PANTONE Hexachrome-style tint ramps أو gamma-corrected density curves أو tone curves مطابقة للمطبعة

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).

القيمة المعادة: اسم colour-space مولد تلقائيًا (Sep1, Sep2, ...). يشترك مدخل Separation مع سجل RegisterSeparation، لذلك تزيد الأسماء تتابعيًا عبر النوعين. يعيد سلسلة فارغة عندما يكون StrictVersionLock مفعّلًا وVersion النشطة أقل من PDF 1.3؛ وإلا يرفع إصدار المستند تلقائيًا إلى 1.3

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;