TLabel : Semi Transparent

A TLabel has a "Transparent" property.

What do you mean by "semi" transparent?

JB

Maybe older versions of Delphi don't have the Transparent property???  In that case, you can write onto any canvas without erasing the background as follows:

    SetBkMode(ACanvas.Handle, TRANSPARENT);
    ACanvas.TextOut(2, 2, 'This is transparent text.');
    SetBkMode(ACanvas.Handle, OPAQUE);

Regards,
JB

Do you want semitransparent text or background or both?

Either way you will have to work with an intermediate bitmap and some pixel-twiddling...

/// John

if its a component, then this will work (should).

ControlStyle := ControlStyle - [csOpaque];

I think JimBob's answer is OK

Thank you for your comment.

I want try to explain about "semi" transparent.
If I have a background (using TImage) and I put a label (the color property filled with black color) in the front of TImage.
If Transparent property is True so the black color will lost.
"Semi" I mean, we are still look the background through a label but the black color not lost.
I give the example if we want to shutdown Windows or if you know Eidos's Championship Manager (Soccer Games Strategy).

Thank you.

Do you simply want dithering or true semitransparence?
When Windows shuts down it uses $AA$55 dithering.

/// John

Note: true semitransparence looks best in hi- to true-color modes and can be difficult to achieve in 16-32768 color modes.
Dithering can be made quite goodlooking in any mode (2-48 bit).

/// John

Quite a good solution. Terribly slow though.
If you, joely, confirm this to be the semitransparence you're looking for, I might just send you some pointers on how to make it faster.

/// John

How to make it faster ?

Sorry it took me so long.

I didn't remember the quick way last night.  This is the fast method (Windows API).  The effect property doesn't nee to be published, but it gives the component a lot more usability.

Try this instead:

unit STLabel;

interface

uses
  Windows, Classes, StdCtrls;

type

   TEffect=(teBlackness,teDSTInvert,teMergeCopy,teMergePaint,teNotSRCCopy,
      teNotSRCErase,tePATCopy,tePATInvert,tePATPaint,teSRCAnd,teSRCCopy,
      teSRCErase,teSRCInvert,teSRCPaint,teWhiteness);

  TSTLabel = class(TLabel)
  private
    fEffect:TEffect;
  protected
    procedure Paint; Override;
    procedure SetEffect(Value:TEffect);
  public
    constructor Create(AOwner:TComponent); override;
  published
    property Effect:TEffect read fEffect write SetEffect;
  end;

procedure Register;

implementation

uses Graphics;

const Effects:array[TEffect] of Integer=(BLACKNESS,DSTINVERT,MERGECOPY,
         MERGEPAINT,NOTSRCCOPY,NOTSRCERASE,PATCOPY,PATINVERT,PATPAINT,
         SRCAND,SRCCOPY,SRCERASE,SRCINVERT,SRCPAINT,WHITENESS);

constructor TSTLabel.Create(AOwner:TComponent);
begin
   inherited Create(AOwner);
   Transparent:=True;
   fEffect:=teSRCPaint;
end;

procedure TSTLabel.Paint;
var Bmp1:TBitmap;
begin
  Bmp1:=TBitmap.Create;
  Bmp1.width:=Width;
  Bmp1.Height:=Height;
  Bmp1.Canvas.Brush.Style:=bsSolid;
  Bmp1.Canvas.Brush.Color:=Color;
  Bmp1.Canvas.FillRect(Rect(0,0,Width,Height));
  BitBLT(Bmp1.Canvas.Handle,0,0,Width,Height,Canvas.Handle,0,0,Effects[fEffect]);
  Canvas.Draw(0,0,Bmp1);
  inherited;
end;

procedure TSTLabel.SetEffect(Value:TEffect);
begin
   if fEffect<>Value then
   begin
      fEffect:=Value;
      Refresh;
   end;
end;

procedure Register;
begin
  RegisterComponents('Samples', [TSTLabel]);
end;

end.

1. Effect property with teSRCPaint is not working for black    color. Why is that?
2. How to reduce color intensity (using teSRCPaint because I       think this effect better than the other, espesially for red      and blue color). What I mean is this component will be more      transparent so the background will be more visible.

Hi joley

1.- The component is doing an or function and black is 0.  Try using SRCAND and an almost white instead;

2.- Change the color.  What you do using SRCPAINT is to increase a particular color.  If you choose clRed (That's RGB (255,0,0))  It will look red.  Try the color RGB(216,0,0) or even lower.  For Delphi clRed is $000000FF, clGreen id $0000FF00 and clBlue is $00FF0000.


Ok, here you can find what Delphi says the effects do:

Value      Description
BLACKNESS      Fills the destination rectangle using the color associated with index 0 in the physical palette. (This color is black for the default physical palette.)

DSTINVERT      Inverts the destination rectangle.

MERGECOPY      Merges the colors of the source rectangle with the specified pattern by using the Boolean AND operator.

MERGEPAINT      Merges the colors of the inverted source rectangle with the colors of the destination rectangle by using the Boolean OR operator.

NOTSRCCOPY      Copies the inverted source rectangle to the destination.

NOTSRCERASE      Combines the colors of the source and destination rectangles by using the Boolean OR operator and then inverts the resultant color.

PATCOPY      Copies the specified pattern into the destination bitmap.

PATINVERT      Combines the colors of the specified pattern with the colors of the destination rectangle by using the Boolean XOR operator.

PATPAINT      Combines the colors of the pattern with the colors of the inverted source rectangle by using the Boolean OR operator. The result of this operation is combined with the colors of the destination rectangle by using the Boolean OR operator.

SRCAND      Combines the colors of the source and destination rectangles by using the Boolean AND operator.

SRCCOPY      Copies the source rectangle directly to the destination rectangle.

SRCERASE      Combines the inverted colors of the destination rectangle with the colors of the source rectangle by using the Boolean AND operator.

SRCINVERT      Combines the colors of the source and destination rectangles by using the Boolean XOR operator.

SRCPAINT      Combines the colors of the source and destination rectangles by using the Boolean OR operator.

WHITENESS      Fills the destination rectangle using the color associated with index 1 in the physical palette. (This color is white for the default physical palette.)