瓷砖/中心图像在窗体背景 [英] Tile/Center image in the forms background

问题描述

还有，我需要将其他组件置于图像。

我尝试过rmControls，但我无法在图像之上放置任何东西。

解决方案

您可以在窗体的 OnPaint 处理程序中绘制图像。以下是一个简单的平铺示例：

  procedure TMyForm.FormPaint（Sender：TObject）; 
 var 
位图：TBitmap; 
左，顶：整数; 
 begin 
 Bitmap：= TBitmap.Create; 
尝试
 Bitmap.LoadFromFile（'C：\desktop\bitmap.bmp'）; 
左：= 0; 
，而Left< Width do begin 
顶部：= 0; 
，而顶部< Height do begin 
 Canvas.Draw（Left，Top，Bitmap）; 
 inc（Top，Bitmap.Height）; 
结束
 inc（Left，Bitmap.Width）; 
结束
最后
 Bitmap.Free; 
结束; 
结束
  

在实际的代码中，您希望缓存位图，而不是每次加载它。我相信你可以制定出如何适应这一点，使其位于中心位置。

输出如下所示：

然而，因为这是表格的背景，所以在处理程序中执行 WM_ERASEBACKGROUND 的绘画要好得多。这也将确保您调整大小时不会有任何闪烁。这是一个更高级的程序版本，演示了这个，以及一个拉伸选项。

 程序TMyForm.FormCreate（发件人： TObject）; 
 begin 
 FBitmap：= TBitmap.Create; 
 FBitmap.LoadFromFile（'C：\desktop\bitmap.bmp'）; 
结束
 
 procedure TMyForm.RadioGroup1Click（Sender：TObject）; 
 begin 
无效; 
结束
 
 procedure TMyForm.FormResize（Sender：TObject）; 
 begin 
 //拉伸绘图需要
无效; 
结束
 
程序TMyForm.PaintTile（Canvas：TCanvas）; 
 var 
 Left，Top：Integer; 
 begin 
左：= 0; 
，而Left< Width do begin 
顶部：= 0; 
，而顶部< Height do begin 
 Canvas.Draw（Left，Top，FBitmap）; 
 inc（Top，FBitmap.Height）; 
结束
 inc（Left，FBitmap.Width）; 
结束
结束
 
程序TMyForm.PaintStretch（Canvas：TCanvas）; 
 begin 
 Canvas.StretchDraw（ClientRect，FBitmap）; 
结束
 
 procedure TMyForm.WMEraseBkgnd（var Message：TWmEraseBkgnd）; 
 var 
画布：TCanvas; 
 begin 
 Canvas：= TCanvas.Create; 
尝试
 Canvas.Handle：= Message.DC; 
 case RadioGroup1.ItemIndex 
 0：
 PaintTile（Canvas）; 
 1：
 PaintStretch（Canvas）; 
结束
最后
 Canvas.Free; 
结束; 
 Message.Result：= 1; 
结束
  

Is there a way to place an image in the form background and be able to tile it or center it ?

Also I need to place other components on top of the image.

I tried rmControls but I cannot place anything on top of the image.

解决方案

You can paint your image in an OnPaint handler for the form. Here's a simple example of tiling:

procedure TMyForm.FormPaint(Sender: TObject);
var
  Bitmap: TBitmap;
  Left, Top: Integer;
begin
  Bitmap := TBitmap.Create;
  Try
    Bitmap.LoadFromFile('C:\desktop\bitmap.bmp');
    Left := 0;
    while Left<Width do begin
      Top := 0;
      while Top<Height do begin
        Canvas.Draw(Left, Top, Bitmap);
        inc(Top, Bitmap.Height);
      end;
      inc(Left, Bitmap.Width);
    end;
  Finally
    Bitmap.Free;
  End;
end;

In real code you would want to cache the bitmap rather than load it every time. I'm sure you can work out how to adapt this to centre a bitmap.

The output looks like this:

However, since this is the background to the form, it's much better to do the painting in a handler for WM_ERASEBACKGROUND. That will also make sure that you won't have any flickering when you resize. Here's a more advanced version of the program that demonstrates this, together with a stretch draw option.

procedure TMyForm.FormCreate(Sender: TObject);
begin
  FBitmap := TBitmap.Create;
  FBitmap.LoadFromFile('C:\desktop\bitmap.bmp');
end;

procedure TMyForm.RadioGroup1Click(Sender: TObject);
begin
  Invalidate;
end;

procedure TMyForm.FormResize(Sender: TObject);
begin
  //needed for stretch drawing
  Invalidate;
end;

procedure TMyForm.PaintTile(Canvas: TCanvas);
var
  Left, Top: Integer;
begin
  Left := 0;
  while Left<Width do begin
    Top := 0;
    while Top<Height do begin
      Canvas.Draw(Left, Top, FBitmap);
      inc(Top, FBitmap.Height);
    end;
    inc(Left, FBitmap.Width);
  end;
end;

procedure TMyForm.PaintStretch(Canvas: TCanvas);
begin
  Canvas.StretchDraw(ClientRect, FBitmap);
end;

procedure TMyForm.WMEraseBkgnd(var Message: TWmEraseBkgnd);
var
  Canvas: TCanvas;
begin
  Canvas := TCanvas.Create;
  Try
    Canvas.Handle := Message.DC;
    case RadioGroup1.ItemIndex of
    0:
      PaintTile(Canvas);
    1:
      PaintStretch(Canvas);
    end;
  Finally
    Canvas.Free;
  End;
  Message.Result := 1;
end;

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