Introduction: Database Interaction

With LEADTOOLS, you can use a variety of strategies to maintain images in a database. This variety is necessary because of the uneven support for storing images using different development and database systems.

The simplest database support is with Visual Basic, where you can bind a LEAD control (ActiveX) to a data control. You can associate the LEAD control with a long binary field in the database, and let the data control handle all of the database maintenance and navigation.

For other systems with ActiveX support, you may be able to use ODBC (Open Database Connectivity). ODBC is a standard interface for accessing local and remote databases. To use it, you define a data source that is implemented with an ODBC driver; then you access the data source in the same way you would a local database. LEADTOOLS provides ActiveX methods and properties that let you directly access image data through an ODBC data source. There are a couple of limitations in this approach. First, since the ActiveX accesses the image data directly and does not access any other data in the record, you must deal with the problem of identifying the image. To solve this problem, you can use another means of selecting records; then synchronize the ActiveX's view, so that it is always accessing the same record. (The ActiveX tutorials describe how to do this.) The second limitation is with ODBC drivers. Most of the available ODBC drivers do not properly support access to long binary fields. (The ACCESS 7.0 and FoxPro 2.x drivers have been tested successfully and are described in the ActiveX tutorials.)

Also, for systems with ActiveX support, you can use OLE DB and ADO to access data. You can bind the LEADTOOLS OLE DB Control to an OLE DB data source, such as the Microsoft ADO Data Control. You can associate the LEADTOOLS OLE DB Control with a long binary field in the database, and let the data control handle all of the database maintenance and navigation.

The LEAD VCL uses a standard approach to data binding, by binding to a DataSet object through a DataSource object. For an overview of data binding, refer to your Delphi or Builder documentation.

You can also use the LEAD VCL with the ODBC. To do this you configure data sources using ODBC, select a database file with the required fields, set the DatabaseName property to the required database source, and set the TableName property to the specified table. You will also need a DataSource object to link the LEAD VCL Main Control to the Table object.

A more flexible approach on lower-level development systems, such as C, C++, and Delphi, is to use the ability of LEADTOOLS to save a file in memory. Once the image is available in memory in a compressed file format, you can use your choice of database engines to store and retrieve the data.

Finally, you may want to consider using your computer's or network's file system to store the images, use a database to store the file paths as strings, and write your own code to do the synchronization. In some cases, this could be a better solution than storing the images directly in the database.