delphi - 在lazarus或delphi中调整图像大小？

Question

我目前正在使用 lazarus 在 pascal 中制作桌面屏幕截图，屏幕截图可以正常工作，但它只显示桌面的左上角。我将其设置为在 TImage 上显示较小的桌面图像。我尝试使用 MyBitmap.width := Round(370) 和 MyBitmap.Height := Round(240);

但是这些都不起作用。

unit Unit1;

{$mode objfpc}{$H+}

interface

uses
  Classes, SysUtils, FileUtil, Forms, Controls, Graphics, Dialogs, ExtCtrls,
  StdCtrls, LCLIntf, LCLType;

type

  { TForm1 }

  TForm1 = class(TForm)
    Button1: TButton;
    Image1: TImage;
    procedure Button1Click(Sender: TObject);

  private
    { private declarations }
  public
    { public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.lfm}

{ TForm1 }



procedure TForm1.Button1Click(Sender: TObject);

  var
    MyBitmap : Tbitmap;
    ScreenDC: HDC;


begin


  try
  MyBitmap := TBitmap.Create;
  ScreenDC := GetDC(0);
  MyBitmap.LoadFromDevice(ScreenDC);
  MyBitmap.Width := Round(370);
  Mybitmap.Height := Round(240);
  ReleaseDC(0, ScreenDC);
  Image1.Picture.Bitmap.Assign(MyBitmap);
  finally
    MyBitmap.free;
  end;





end;

end. 

Answer 1

将 LoadFromDevice 替换为

MyBitmap.SetSize(370, 240); 
StretchBlt(MyBitmap.Canvas.Handle, //destination HDC
  0, 0, 370, 240, // destination size
  ScreenDC, //source HDC
  0, 0, Screen.Width, Screen.Height, // source size
  SrcCopy 
  );

在现有位图上设置较小的尺寸只会将其裁剪。
您的目的是缩放位图。

The StretchBlt function copies a bitmap from a source rectangle into a destination rectangle, stretching or compressing the bitmap to fit the dimensions of the destination rectangle, if necessary. The system stretches or compresses the bitmap according to the stretching mode currently set in the destination device context.