TIEBitmap.CanvasCurrentAlpha

Declaration

property CanvasCurrentAlpha: integer

Description

Setting this property to a value >=0, makes the alpha channel an 8 bit gray scale paintable bitmap.
This means that you can draw on the alpha channel using TCanvas object.
The value (0..255) specifies the transparency, 0=fully transparent, 255=fully opaque.



Default: -1

Examples

ImageEnView1.IEBitmap.AlphaChannel.CanvasCurrentAlpha := 128;
with ImageEnView1.IEBitmap.AlphaChannel.Canvas do
begin
  FillRect(0, 0, 100, 100);
  Ellipse(10, 10, 200, 200);
end;

// Draw a line on the IEBitmap canvas and ensure it also make opaque on the transparency
With ImageEnView1 do
begin
  IEBitmap.Canvas.Pen.Color := clRed;
  IEBitmap.Canvas.MoveTo( 10, 10 ) ;
  IEBitmap.Canvas.LineTo( 100, 100 );

  IEBitmap.AlphaChannel.CanvasCurrentAlpha := 255;
  IEBitmap.AlphaChannel.Canvas.MoveTo( 10, 10 ) ;
  IEBitmap.AlphaChannel.Canvas.LineTo( 100, 100 );

  Update();
end

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