Mega Code Archive
Give your forms a background
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Web pages use tiled bitmaps to create backgrounds. Is it possible to do this in Delphi?
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Before I learned how to do this, to create a background on a form, I'd drop a TImage on my form, then set its Align property to alClient. For low-resolution bitmaps, the pixelation that would occur at times was absolutely terrible! But with the method that I'll show you here (Note: this is merely ONE way of doing it), you can easily tile bitmaps on the surface of your form. The trick is in trapping the WM_ERASEBKGND message in a handler, creating a bitmap at runtime, then writing a quick bit of code in the OnPaint event handler. Let's go through the steps.
In the private section of your code place the following:
private
{ Private declarations }
MyBitmap: TBitmap;
procedure WMEraseBkgnd(var m: TWMEraseBkgnd);
message WM_ERASEBKGND;
Notice the declaration of MyBitmap. We'll be creating an instance for it below. The message handler for WM_ERASEBKGND looks like this:
procedure TBmpform.WMEraseBkgnd(var m : TWMEraseBkgnd);
begin
m.Result := LRESULT(False);
end;
Then, create the following code for the OnPaint event handler Note: In the original article, the "x := x + MyBitmap.Width" is a bit inefficient in that continuously accessing the Bitmap.Width or .Height properties can slow things down - especially when you've got code in the OnPaint method. So what I did here was to simply set a couple of variables to store the Width and Height property values of the bitmap.
procedure TBmpForm.FormPaint(Sender: TObject);
var
x, y: Integer;
iBMWid, iBMHeight : Integer;
begin
iBMWid := MyBitmap.Width;
iBMHeight := MyBitmap.Height;
y := 0;
while y < Height do
begin
x := 0;
while x < Width do
begin
Canvas.Draw(x, y, MyBitmap);
x := x + iBMWid;
end;
y := y + iBMHeight;
end;
end;
Finally, create an instance of the bitmap you want to tile in the background in the OnCreate event of your form:
procedure TForm1.FormCreate(Sender: TObject);
begin
Application.OnHint := ShowHint;
MyBitmap := TBitmap.Create;
MyBitmap.LoadFromFile('Brick4.bmp');
end;
Whoops, almost forgot! You need to destroy the bitmap when you exit!
procedure TForm1.FormClose(Sender: TObject;
var Action: TCloseAction);
begin
Action := caFree;
bmpBackground.Free;
end;
Well, that's it. Don't you just love the quick and dirty ones?
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