Declarations

procedure Blur32(ASource, ADest: TBitmap32; Radius: TFloat); overload;
procedure Blur32(Bitmap: TBitmap32; Radius: TFloat); overload;
procedure Blur32(Bitmap: TBitmap32; Radius: TFloat; const Bounds: TRect); overload;
procedure Blur32(Bitmap: TBitmap32; Radius: TFloat; const Region: TArrayOfFloatPoint); overload;

Overload Details

Overload 1

procedure Blur32(ASource, ADest: TBitmap32; Radius: TFloat); overload;

Blurs the source bitmap and writes the result into the destination bitmap.

Parameter	Type	Description
ASource	TBitmap32	Source 32-bit bitmap to read pixels from.
ADest	TBitmap32	Destination 32-bit bitmap to receive the blurred output.
Radius	TFloat	Blur radius in pixels.

Overload 2

procedure Blur32(Bitmap: TBitmap32; Radius: TFloat); overload;

Blurs the entire bitmap in-place.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap to blur in-place.
Radius	TFloat	Blur radius in pixels.

Overload 3

procedure Blur32(Bitmap: TBitmap32; Radius: TFloat; const Bounds: TRect); overload;

Blurs a rectangular sub-region of a bitmap in-place.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap containing the sub-region to blur.
Radius	TFloat	Blur radius in pixels.
Bounds	TRect	Bounding rectangle defining the target sub-region.

Overload 4

procedure Blur32(Bitmap: TBitmap32; Radius: TFloat; const Region: TArrayOfFloatPoint); overload;

Blurs an arbitrary polygonal region of a bitmap in-place.

Parameter	Type	Description
Bitmap	TBitmap32	Bitmap containing the polygonal region to blur.
Radius	TFloat	Blur radius in pixels.
Region	TArrayOfFloatPoint	Array of 2D floating-point points defining the polygon vertices.

Description

Blur32 performs spatial Gaussian blurring on 32-bit ARGB bitmaps using a high-performance Infinite Impulse Response (IIR) recursive Gaussian filter.

The filter execution time is $O(1)$ per pixel, making performance independent of the specified Radius.

Radius Threshold

If Radius is less than Blur32MinRadius (default $0.5$ pixels), Blur32 skips filter calculations. For out-of-place calls (ASource, ADest), ASource is copied directly to ADest. For in-place calls, the procedure exits immediately.

Channel Processing

All four color channels (Red, Green, Blue, Alpha) are processed. Blurring the Alpha channel produces smooth antialiased region borders and drop shadows.

Example

var
  Bmp: TBitmap32;
begin
  Bmp := TBitmap32.Create;
  try
    Bmp.LoadFromFile('input.png');

    // Blur entire bitmap in-place with a 5.0 pixel Gaussian radius
    Blur32(Bmp, 5.0);

    Bmp.SaveToFile('blurred.png');
  finally
    Bmp.Free;
  end;
end;

See also

• GammaBlur32
• HorizontalBlur32
• GaussianRadiusToSigma
• Blur32MinRadius