unit1.~pas

Delphi图像数据的压缩处理 Delphi图像数据的压缩处理 Delphi图像数据的压缩处理

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms, Dialogs,
  StdCtrls, ZLib;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure GetScreen(var Bmp: TBitmap);
var
  Dc: HDC;
  MyCanvas: TCanvas;
  MyRect: TRect;
begin
  Dc := GetWindowDC(0);
  MyCanvas := TCanvas.Create;
  try
    MyCanvas.Handle := Dc;
    MyRect:=Rect(0,0,Screen.Width, Screen.Height);
    //图像为 24位真彩色，也可根据实际需要调整
    Bmp.PixelFormat := pf24bit;
    Bmp.Width := MyRect.Right;
    Bmp.Height := MyRect.Bottom;
    //捕捉整个屏幕图像
    Bmp.Canvas.CopyRect(MyRect, MyCanvas, MyRect);
  finally
    MyCanvas.Handle := 0;
    MyCanvas.Free;
    ReleaseDC(0, Dc);
  end;
end;

procedure CompressBitmap(var CompressedStream: TMemoryStream;const CompressionLevel: TCompressionLevel);
var
  SourceStream: TCompressionStream;
  DestStream: TMemoryStream;
  Count: Integer;
Begin
  //获得图像流的原始尺寸
  Count := CompressedStream.Size;
  DestStream := TMemoryStream.Create;
  SourceStream:=TCompressionStream.Create(CompressionLevel, DestStream);
  Try
    //SourceStream中保存着原始的图像流
    CompressedStream.SaveToStream(SourceStream);
    //将原始图像流进行压缩， DestStream中保存着压缩后的图像流
    SourceStream.Free;
    CompressedStream.Clear;
    //写入原始图像的尺寸
    CompressedStream.WriteBuffer(Count, SizeOf(Count));
    //写入经过压缩的图像流
    CompressedStream.CopyFrom(DestStream, 0);
  finally
    DestStream.Free;
  end;
end;

procedure UnCompressBitmap(const CompressedStream: TFileStream; var Bmp: TBitmap);
var
  SourceStream: TDecompressionStream;
  DestStream: TMemoryStream;
  Buffer: PChar;
  Count: Integer;
Begin
  //从被压缩的图像流中读出原始图像的尺寸
  CompressedStream.ReadBuffer(Count, SizeOf(Count));
  //根据图像尺寸大小为将要读入的原始图像流分配内存块
  GetMem(Buffer, Count);
  DestStream := TMemoryStream.Create;
  SourceStream := TDecompressionStream.Create(CompressedStream);
  Try
    //将被压缩的图像流解压缩，然后存入 Buffer内存块中
    SourceStream.ReadBuffer(Buffer^, Count);
    //将原始图像流保存至 DestStream流中
    DestStream.WriteBuffer(Buffer^, Count);
    DestStream.Position := 0;//复位流指针
    //从 DestStream流中载入原始图像流
    Bmp.LoadFromStream(DestStream);
  finally
    FreeMem(Buffer);
    DestStream.Free;
  end;
end;

procedure TForm1.Button1Click(Sender: TObject);
var
  Bmp: TBitmap;
  CompressedStream: TMemoryStream;
begin
  Bmp := TBitmap.Create;
  CompressedStream := TMemoryStream.Create;
  Try
    //捕获当前整个屏幕 ,将图像保存至 Bmp对象中
    GetScreen(Bmp);
    //将 Bmp对象中的图像保存至内存流中
    Bmp.SaveToStream(CompressedStream);
    //按缺省的压缩比例对原始图像流进行压缩
    CompressBitmap(CompressedStream, clDefault);
    //将压缩之后的图像流保存为自定义格式的文件
    CompressedStream.SaveToFile('C:\cj.dat');
  finally
    Bmp.Free;
    CompressedStream.Free;
  end;
end;

procedure TForm1.Button2Click(Sender: TObject);
var
  CompressedStream: TFileStream;
  Bmp: TBitmap;
begin
  Bmp := TBitmap.Create;
  //以文件流的只读方式打开自定义的压缩格式文件
  CompressedStream := TFileStream.Create('C:\cj.dat' , fmOpenRead);
  Try
    //将被压缩的图像流进行解压缩
    UnCompressBitmap(CompressedStream, Bmp);
    //将原始图像流还原为指定的 BMP文件
    Bmp.SaveToFile('C:\cj.bmp');
  finally
    Bmp.Free;
    CompressedStream.Free;
  end;
end;

end.