你如何提取从TGraphicField位图？

本文介绍了你如何提取从TGraphicField位图？的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我要疯了。

下面是我在做什么。

放入一个TClientDataSet，一个的TImage，并在窗体上一个TButton。

将Clientdataset1.Filename到biolife.xml

按钮双击并添加下列code：

程序TForm31.Button1Click（发件人：TObject的）;VAR  BF：TBlobField;  BS：TStream;  BM：TBitmap;开始  ClientDataset1.Open;  ClientDataset1.First;  BF：= ClientDataSet1.FieldByName（'平面'）作为TBlobField;  BS：= ClientDataSet1.CreateBlobStream（BF，bmRead）;  BS.Position：= 0;  BM：= TBitmap.Create;  尝试    BM.LoadFromStream（BS）;  最后    BM.Free;  结束;结束;

运行它。当我这样做，我得到位图图像无效。

咦？该数据一直是位年 - ？什么是错

解决方案   

图形字段是二进制大对象（BLOB）领域，其中的一种形式  在数据包括BLOB头描述的编码  图形化的价值。

BLOB头是误导那里，它似乎是图形备忘录悖论存储格式的残余。

（*从DB *）{悖论图形BLOB头}类型  TGraphicHeader =记录    字数：字; {1}固定    HTYPE：字; {在$ 0100固定}    尺寸：Longint型; {尺寸不包括报头}  结束;程序TForm1.FormClick（发件人：TObject的）;常量  HeaderSize =中SizeOf（TGraphicHeader）;VAR  现场：TGraphicField;  流：TClientBlobStream;开始  现场：= ClientDataSet1.FieldByName（'平面'）作为TGraphicField;  流：= ClientDataSet1.CreateBlobStream（场，bmRead）为TClientBlobStream;  Stream.SaveToFile（'dump.bin'）; //检查BLOB，看到额外的字节preceding BITMAPFILEHEADER  断言（Stream.Position = 0）;  Stream.Seek（+ HeaderSize，soFromCurrent）; //丢弃报头，它不包含使用任何反正  Image1.Picture.Bitmap.LoadFromStream（流）;  ClientDataSet1.Next;结束;

I am going nuts.

Here's what I am doing

Drop a TClientDataset, a TImage, and a TButton on a form.

Set the Clientdataset1.Filename to biolife.xml

Double click on the button and add the following code:

procedure TForm31.Button1Click(Sender: TObject); var BF: TBlobField; BS: TStream; BM: TBitmap; begin ClientDataset1.Open; ClientDataset1.First; BF := ClientDataSet1.FieldByName('Graphic') as TBlobField; BS := ClientDataSet1.CreateBlobStream(BF, bmRead); BS.Position := 0; BM := TBitmap.Create; try BM.LoadFromStream(BS); finally BM.Free; end; end;

Run it. When I do, I get "Bitmap image is not valid".

Huh? That data has been a bitmap for years -- what is wrong?

解决方案

Graphics fields are a form of binary large object (BLOB) field where the data includes a BLOB header describing the encoding of the graphical value.

"BLOB header" is misleading there, it appears to be a remnant of Paradox storage format for graphic memos.

(* from DB *) { Paradox graphic BLOB header } type TGraphicHeader = record Count: Word; { Fixed at 1 } HType: Word; { Fixed at $0100 } Size: Longint; { Size not including header } end; procedure TForm1.FormClick(Sender: TObject); const HeaderSize = SizeOf(TGraphicHeader); var Field: TGraphicField; Stream: TClientBlobStream; begin Field := ClientDataSet1.FieldByName('Graphic') as TGraphicField; Stream := ClientDataSet1.CreateBlobStream(Field, bmRead) as TClientBlobStream; Stream.SaveToFile('dump.bin'); // examine BLOB and see extra bytes preceding BITMAPFILEHEADER Assert(Stream.Position = 0); Stream.Seek(+HeaderSize, soFromCurrent); // discard header, it does not contain anything of use anyways Image1.Picture.Bitmap.LoadFromStream(Stream); ClientDataSet1.Next; end;