Delphi中TMemoryStream的用法

淡淡的烟草味﹌ 2021-11-22 08:02 588阅读 0赞

1.文件流 TStreamMemoery 读写内存

var  
    	BitmapMemoryStream:TMemoryStream;  
    	Bitmap1:TBitmap;  
      
    procedure TForm.Button1Click(Sender:TObject);  
    begin  
    	BitmapmemroyStream:=TmemoryStream.Create; file://建立MemoryStream  
    	Bitmap1:=TBitmap.Create;  
    	try  
    		Bitmap1.LoadFromFile(’d:\Bitmap1.bmp’);  
    	except  
    		ShowMessage(’Error On LoadFile bitmap1.bmp’);  
    	end;  
    end;   
      
    procedure TForm.Button2Click(Sneder:Tobject);  
    begin  
    	if Assigned(Bitmap1) then  
    	Bitmap1.SaveToStream(BitmapmemoryStream);  
    end;  
      
    procedure TForm.Button3Click(Sender:TObject);  
    begin  
    	if BitmapMemoryStream<>nil then  
    	begin  
    		try  
    			BitmapMemroyStream.SaveToFile(’Bitmap1.str’); file://内存流保存，大小与  file://Bitmap1.bmp一样  
    		except  
    			showmessage(’error on access memory!’);  
    		end;  
    	end;  
    end;  
      
    procedure TForm.Button4Click(Sender:TObject);  
    var  
    	Buffer:Array[0..53] of char;  
    begin  
    	if Assigned( BitmapMemroyStream) then  
    	try  
    		BitmapMemroyStream.Seek(0,soFromBeginning);  
    		BitmapMemoryStream.Read(Buffer,54);  
    	if Buffer[0]=’B’ and Buffer[1]=’M’ then file://改写内存内容  
    	begin  
    		BitmapMemoryStream.Seek(0,soFromBeginning);  
    		BitmapmemoryStream.Write(’ICE’,3);   
    		Button3Click(Sender);//将改写的内容写入文件  
    	end;  
    	except  
    		ShowMessage(’error On Access memroyStream’);  
    	end;  
    end;

2.如何将一个流的内容写入到剪贴板中，并处理

var  
    	hbuf : THandle;  
    	bufptr : Pointer;  
    	mstream : TMemoryStream;  
    begin  
    	mstream := TMemoryStream.Create;  
    	try  
    		{-- 处理流的代码 --}  
    		hbuf := GlobalAlloc(GMEM_MOVEABLE, mstream.size);  
    	try  
    		bufptr := GlobalLock(hbuf);  
    		try  
    			Move(mstream.Memory^, bufptr^, mstream.size);  
    			Clipboard.SetAsHandle(CF_MYFORMAT, hbuf);  
    		finally  
    			GlobalUnlock(hbuf);  
    		end;  
    	except  
    		GlobalFree(hbuf);  
    		raise;  
    	end;  
    	finally  
    		mstream.Free;  
    	end;  
    end;  
    //请注意不要将分配的全局缓冲区释放，这个工作由剪贴板来完成，在读出数据中  
    //你应该将它复制后处理。  
      
    //将剪贴板内容读出来  
    var  
    	hbuf : THandle;  
    	bufptr : Pointer;  
    	mstream : TMemoryStream;  
    begin  
    	hbuf := Clipboard.GetAsHandle(CF_MYFORMAT);  
    	if hbuf <> 0 then begin  
    		bufptr := GlobalLock(hbuf);  
    		if bufptr <> nil then begin  
    			try  
    				mstream := TMemoryStream.Create;  
    				try  
    					mstream.WriteBuffer(bufptr^, GlobalSize(hbuf));  
    					mstream.Position := 0;  
    					{-- 处理流的代码 --}  
    				finally  
    					mstream.Free;  
    				end;  
    			finally  
    				GlobalUnlock(hbuf);  
    			end;  
    		end;  
    	end;  
    end;

3.在Dephi中使用TStream读写数据的技巧

a.btnRead的Click事件，这里演示了TFileStream的用法。

var  
        MS: TFileStream;  
    begin  
        if OpenDialog1.Execute then  
        begin  
            MS:=TFileStream.Create  
            (OpenDialog1.FileName, fmOpenRead);  
            Image1.Picture.Bitmap.LoadFromStream(MS);  
            MS.Free;  
        end;  
    end;

b.btnInvert的Click事件，这里演示了TMemoryStream的用法。其中使用了Invert函数，这是一个简单的将图象反色的函数（仅对真彩图象有效），它返回一个指向处理过的图象数据块的指针。

var  
    	MS: TMemoryStream;  
    	pImage: pointer;  
    begin  
    	MS:=TMemoryStream.create;  
    	Image1.Picture.Bitmap.SaveToStream(MS);  
    	MS.Position:=0;  
    	pImage:=Invert(MS.Memory, MS.size);   //file://Memory属性是指向实际内存块的指针  
    	MS.Write(pImage^,MS.size);  
    	MS.Position:=0;   //file://上一行代码使指针移到了Stream末尾，所以要复位  
    	Image1.Picture.Bitmap.LoadFromStream(MS);  
    	FreeMem(pImage);   
    	MS.Free;  
    end;  
      
    //Invert函数如下：  
    function TForm1.Invert(pImage: pointer; size: Integer): pointer;  
    var  
    	pData, pMem: PChar;  
    	i: Integer;  
    begin  
    	pMem:=AllocMem(size);  
    	CopyMemory(pMem,pImage,size);  
    	pData:=pMem+54;  
    	for i:=0 to size-54-1 do  
    	begin  
    		pData^:=Char(not integer(pData^));  
    		pData:=pData+1;  
    	end;  
    	Result:=pMem;  
    end;

c.btnSave的Click事件，这里演示了TMemoryStream的另一种用法，将Stream中的数据写到数据库

var  
        MS: TMemoryStream;  
    begin  
        MS:=TMemoryStream.create;  
        Image1.Picture.Bitmap.SaveToStream(MS);  
        MS.Position:=0;  
        Table1.Append;   
        file://在数据库中添加一条记录  
        TBlobField(Table1.FieldbyName  
        (’image’)).LoadFromStream(MS);  
        Table1.Post;   
        file://将所作的更新写入数据库  
    end;

d.DBNavigator1的Click事件，这里演示了TBlobStream的用法，使用了和写入时不同的方法来读出数据库的图象数据。

var  
        MS: TStream;  
    begin  
        with Table1 do  
        MS:=CreateBlobStream  
        (FieldbyName(’image’),bmRead);  
        Image1.Picture.Bitmap.  
        LoadFromStream(MS);  
        MS.Free;  
    end;