Declaration

procedure GammaSelectiveGaussianBlur32(ASource, ADest: TBitmap32; Radius: TFloat; Delta: Integer);

Parameters

Parameter	Type	Description
ASource	TBitmap32	Source 32-bit bitmap to read pixels from.
ADest	TBitmap32	Destination 32-bit bitmap to receive the linear-light blurred output.
Radius	TFloat	Spatial blur radius in pixels.
Delta	Integer	Maximum color channel difference threshold (0..255).

Description

GammaSelectiveGaussianBlur32 performs edge-preserving selective Gaussian blurring in linear light space.

Pixel channels are converted into linear light space before color thresholding and kernel weighting, preventing dark fringe artifacts along high-contrast boundaries.

Behavior Summary

• Linear Light Precision: Performs gamma decoding and encoding via precomputed tables constructed from the current Gamma settings (GAMMA_VALUE, GAMMA_IS_SRGB).
• Detail Preservation: Neighbor pixels within Radius are included in the Gaussian average only if their color intensity difference from the reference pixel does not exceed Delta.
• Alpha Channel: The Alpha channel is preserved without being blurred.

Example

var
  Src, Dst: TBitmap32;
begin
  Src := TBitmap32.Create;
  Dst := TBitmap32.Create;
  try
    Src.LoadFromFile('compressed_art.png');

    // Gamma-correct selective blur to smooth artifacts without dark border halos
    GammaSelectiveGaussianBlur32(Src, Dst, 5.0, 20);

    Dst.SaveToFile('compressed_art_clean.png');
  finally
    Src.Free;
    Dst.Free;
  end;
end;

See also

• SelectiveGaussianBlur32
• GammaBlur32
• GR32_Gamma