Delphi accesses JPEG files to the SQL Server database

Delphi accesses JPEG files to the SQL Server database
Ghyghost)
Recently, when I wrote a small student management system, I needed to use the ADO control to access the image of the SQL Server database. I found that most of the operations were performed on BMP files (greatly increasing the database size), but I found★Eagletian★The ADO English technical document translated by experts involves the key technologies used to access JPEG files in databases. It has been tested in WIN98 + SQL Server Desktop edition and runs well. The source code is published as follows:
Unit unit1;

Interface

Uses
Windows, messages, sysutils, classes, graphics, controls, forms, dialogs,
Extctrls, dbctrls, grids, dbgrids, DB, ADODB, JPEG, stdctrls, dbtables;
{The uses JPEG unit is required to enable the storage of JPG files}
Type
Tform1 = Class (tform)
Performance1: tdatasource;
Adoquery1: tadoquery;
Dbgrid1: TDBGrid;
Dbnavigator1: tdbnavigator;
Image1: timage;
Savebutton: tbutton;
Showbutton: tbutton;
Opendialog1: topendialog;
Adoquery1id: tintegerfield;
Adoquery1pic: tblobfield;
Procedure savebuttonclick (Sender: tobject );
Procedure showbuttonclick (Sender: tobject );
Procedure dbnavigator1click (Sender: tobject; button: tnavigatebtn );
Private
{Private Declarations}
Public
{Public declarations}
End;

VaR
Form1: tform1;

Implementation

{$ R *. DFM}

Function compute startsinblob (picfield: tblobfield): integer;
VaR
Ghy: tadoblobstream;
Buffer: word;
HX: string;
Begin
Result: =-1;
Ghy: = tadoblobstream. Create (picfield, bmread );
Try
While (result =-1) and (ghy. Position + 1 begin
Ghy. readbuffer (buffer, 1 );
HX: = inttohex (buffer, 2 );
If HX = 'ff 'Then begin
Ghy. readbuffer (buffer, 1 );
HX: = inttohex (buffer, 2 );
If HX = 'd8' then result: = ghy. Position-2
Else if HX = 'ff' then
Ghy. Position: = ghy. Position-1;
End; // If
End; // while
Finally
Ghy. Free
End; // try
End;

Procedure tform1.savebuttonclick (Sender: tobject );
VaR
Picstream: tadoblobstream;
Begin
Adoquery1.edit;
Picstream: = tadoblobstream. Create (tblobfield (adoquery1.fields [1]), bmwrite );
If form1.opendialog1.exe cute then
Begin
Picstream. loadfromfile (opendialog1.filename );
Picstream. Position: = 0;
Adoquery1.edit;
Tblobfield (adoquery1.fields [1]). loadfromstream (picstream );
Adoquery1.post;
End;

End;

Procedure tform1.showbuttonclick (Sender: tobject );
VaR
Ghy: tadoblobstream;
PIC: Tsung image;
Begin
Ghy: = tadoblobstream. Create (adoquery1pic, bmread );
Try
Ghy. Seek (export startsinblob (adoquery1pic), sofrombeginning );
PIC: = tsf-image. Create;
Try
PIC. loadfromstream (ghy );
Image1.picture. Graphic: = PIC;
Finally
PIC. Free;
End;
Finally
Ghy. Free
End;
End;

Procedure tform1.dbnavigator1click (Sender: tobject; button: tnavigatebtn );
Begin
If Button in [nbfirst, nbprior, nbnext, nblast] Then showbutton. Click;
End;

End.

If the BMP file is to be stored in the database, you can use procedure tform1.showbuttonclick (Sender: tobject). When the code is changed as follows, you can store the operation that displays the BMP file format.
Procedure tform1.showbuttonclick (Sender: tobject );
VaR
Ghy: tadoblobstream;
PIC: tbitmap;
Begin
Ghy: = tadoblobstream. Create (adoquery1pic, bmread );
Try
{Ghy. Seek (export startsinblob (adoquery1pic), sofrombeginning );}
PIC: = tbitmap. Create;
Try
PIC. loadfromstream (ghy );
Image1.picture. Graphic: = PIC;
Finally
PIC. Free;
End;
Finally
Ghy. Free
End;
End;
The specific operations for using Delphi to access JPEG files to the SQL Server database have been described.
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