| 解決思路 |
| 首先利用屏幕拷貝捕捉到當(dāng)前整個屏幕的圖像，然后在內(nèi)存中保存為 BMP文件格式。壓縮時，使用 TComPRessionStream對象對原始圖像進(jìn)行壓縮并且保存為自定義的文件格式；解壓縮時，使用 TDecompressionStream對象對被壓縮的圖像進(jìn)行解壓縮，還原為 BMP格式的圖像文件。 |
| 具體實現(xiàn) |
| 新建一個項目文件，在主單元的接口部分引用 Zlib.pas，在主表單上放置兩個按鈕 Button1、 Button2，在它們的 OnClick事件中寫上相應(yīng)的過程調(diào)用代碼。 |
| 部分程序源代碼如下： |
| 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} |
| 1．捕捉全屏幕圖像 |
| 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); |
| //圖像為 24位真彩色，也可根據(jù)實際需要調(diào)整 |
| Bmp.PixelFormat := pf24bit; |
| Bmp.Width := MyRect.Right; |
| Bmp.Height := MyRect.Bottom; |
| //捕捉整個屏幕圖像 |
| Bmp.Canvas.CopyRect(MyRect, MyCanvas, MyRect); |
| finally |
| MyCanvas.Handle := 0; |
| MyCanvas.Free; |
| ReleaseDC(0, Dc); |
| end; |
| end; |
| 2．壓縮圖像 |
| procedure CompressBitmap(var CompressedStream: TMemoryStream;const CompressionLevel: TCompressionLevel); |
| var |
| SourceStream: TCompressionStream; |
| DestStream: TMemoryStream; |
| Count: Integer; |
| Begin |
| //獲得圖像流的原始尺寸 |
| Count := CompressedStream.Size; |
| DestStream := TMemoryStream.Create; |
| SourceStream:=TCompressionStream.Create |
| (CompressionLevel, DestStream); |
| Try |
| //SourceStream中保存著原始的圖像流 |
| CompressedStream.SaveToStream(SourceStream); |
| //將原始圖像流進(jìn)行壓縮， DestStream中保存著壓縮后的圖像流 |
| SourceStream.Free; |
| CompressedStream.Clear; |
| //寫入原始圖像的尺寸 |
| CompressedStream.WriteBuffer(Count, SizeOf |
| (Count)); |
| //寫入經(jīng)過壓縮的圖像流 |
| CompressedStream.CopyFrom(DestStream, 0); |
| finally |
| DestStream.Free; |
| end; |
| end; |
| 3．還原被壓縮圖像 |
| procedure UnCompressBitmap(const CompressedStream: TFileStream; var Bmp: TBitmap); |
| var |
| SourceStream: TDecompressionStream; |
| DestStream: TMemoryStream; |
| Buffer: PChar; |
| Count: Integer; |
| Begin |
| //從被壓縮的圖像流中讀出原始圖像的尺寸 |
| CompressedStream.ReadBuffer(Count, SizeOf(Count)); |
| //根據(jù)圖像尺寸大小為將要讀入的原始圖像流分配內(nèi)存塊 |
| GetMem(Buffer, Count); |
| DestStream := TMemoryStream.Create; |
| SourceStream := TDecompressionStream.Create(CompressedStream); |
| Try |
| //將被壓縮的圖像流解壓縮，然后存入 Buffer內(nèi)存塊中 |
| SourceStream.ReadBuffer(Buffer^, Count); |
| //將原始圖像流保存至 DestStream流中 |
| DestStream.WriteBuffer(Buffer^, Count); |
| DestStream.Position := 0;//復(fù)位流指針 |
| //從 DestStream流中載入原始圖像流 |
| Bmp.LoadFromStream(DestStream); |
| finally |
| FreeMem(Buffer); |
| DestStream.Free; |
| end; |
| end; |
| 4．壓縮按鈕 OnClick事件 |
| procedure TForm1.Button1Click(Sender: TObject); |
| var |
| Bmp: TBitmap; |
| CompressedStream: TMemoryStream; |
| begin |
| Bmp := TBitmap.Create; |
| CompressedStream := TMemoryStream.Create; |
| Try |
| //捕獲當(dāng)前整個屏幕 ,將圖像保存至 Bmp對象中 GetScreen(Bmp); |
| //將 Bmp對象中的圖像保存至內(nèi)存流中 |
| Bmp.SaveToStream(CompressedStream); |
| //按缺省的壓縮比例對原始圖像流進(jìn)行壓縮 |
| CompressBitmap(CompressedStream, clDefault); |
| //將壓縮之后的圖像流保存為自定義格式的文件 |
| CompressedStream.SaveToFile(‘ C:cj.dat’ ); |
| finally |
| Bmp.Free; |
| CompressedStream.Free; |
| end; |
| end; |
| 5．解壓縮按鈕 OnClick事件 |
| procedure TForm1.Button2Click(Sender: TObject); |
| var |
| CompressedStream: TFileStream; |
| Bmp: TBitmap; |
| begin |
| Bmp := TBitmap.Create; |
| //以文件流的只讀方式打開自定義的壓縮格式文件 |
| CompressedStream := TFileStream.Create(‘ C:cj.dat’ , fmOpenRead); |
| Try |
| //將被壓縮的圖像流進(jìn)行解壓縮 |
| UnCompressBitmap(CompressedStream, Bmp); |
| //將原始圖像流還原為指定的 BMP文件 |
| Bmp.SaveToFile(‘ C:cj.bmp’ ); |
| finally |
| Bmp.Free; |
| CompressedStream.Free; |
| end; |
| end; |
| 此外 TCompressionStream對象還提供了 CompressionRate屬性，該屬性用于描述對原始數(shù)據(jù)進(jìn)行壓縮后的壓縮比率，而 OnProgress事件在壓縮與解壓縮過程中都會被觸發(fā)，開發(fā)人員可以在該事件中編寫用于顯示進(jìn)度的代碼。 |
| 以上代碼在 Delphi 5.0中調(diào)試運行通過。 |
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