TBitmap德尔福2009年绘制透明图像 [英] TBitmap drawing transparent image in Delphi 2009

问题描述

问题的TBitmap对象上画一个半透明的PNG图像。

Problem in drawing a semi transparent PNG image on TBitmap object.

如果该TBitmap的，HandleType设为bmDDB，则帆布绘制透明。
但问题是它不能在各种机器工作。（为前：在苹果电脑上的Windows）

If the TBitmap's ,HandleType is set to bmDDB, then the canvas is drawn transparent. But the problem is it doesn't work on all kinds of machines (for ex: Windows on apple computers).

当一个TBitmap的HandleType属性设置为bmDIB，画布背景绘制白色。

When a TBitmap's HandleType property is set to bmDIB, canvas background is drawn white.

bmp.HandleType := bmDIB;

我试着刷样式设置为bsCle​​ar。但是，在绘制黑色的透明像素。

I tried setting Brush style to bsClear. But it draws the transparent pixels in black color.

我如何绘制图像preserving其透明度和光滑的弧形边缘。

How can I draw an image preserving its transparency and smooth curved edges.

谢谢
帕文。

推荐答案

这当然是可能的油漆与透明背景的画布一个 bmDIB 位图：

It is certainly possible to paint a bmDIB bitmap with transparent background to a canvas:

procedure TForm1.FormPaint(Sender: TObject);
var
  Bmp: TBitmap;
begin
  Bmp := TBitmap.Create;
  try
    Bmp.PixelFormat := pf32bit;
    Bmp.HandleType := bmDIB;
    Bmp.Width := 700;
    Bmp.Height := 400;
    Bmp.Transparent := TRUE;
    Bmp.TransparentColor := clMaroon;

    with Bmp.Canvas do begin
      Brush.Color := clMaroon;
      FillRect(Rect(0, 0, Bmp.Width, Bmp.Height));

      Brush.Color := clBlue;
      FillRect(Rect(42, 42, 200, 300));
    end;

    Canvas.Draw(12, 12, Bmp);
  finally
    Bmp.Free;
  end;
end;

请注意，整个位图先用颜色设置为 TransparentColor 填写。

Note that the whole bitmap is filled first with the colour set as TransparentColor.

但对于更多的控制和速度，你应该寻找到一个解决方案，而不是依赖于GDI（涉及图形卡和驱动程序的功能），类似的 Graphics32 。

But for more control and speed you should look into a solution that is not as dependent on the GDI (which involves graphics card and driver capabilities), something like Graphics32.

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