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Creating Web Friendly Barcodes (LZW GIF compression)

The TAL ActiveX component has the ability to save bar codes in all major graphic file formats including the GIF file format that is used extensively in web pages. By default, when you save a GIF file using the TAL ActiveX component, it will save the file as an "uncompressed" GIF. GIF files can also use a special data compression algorithm called LZW compression that up until July of 2004 was protected by a Patent held by Unisys Corporation. The size difference between uncompressed and compressed GIF files is typically ten to one therefore you can greatly reduce the size of any bar code image saved as a GIF file by enabling GIF compression in the TAL ActiveX component.

Because of the patent protection of the LZW compression techniques, the TAL ActiveX component would normally not allow you to create LZW compressed GIF files without you first purchasing a special license directly from Unisys. To enforce this, the TAL ActiveX component has two properties that are used to first enable LZW compression in GIF files as well as specify a special "unlock code" that would unlock the LZW compression feature in the TAL Active X component after you purchase the license from Unisys.

Now that the Unisys patent has expired, you are now legally allowed to use LZW compression in GIF files without having to pay a license fee to Unisys however in order to do so, you will need to configure two properties in the TAL ActiveX component that will both enable LZW compression as well as unlock it.

The following steps show how to create LZW compressed GIF files with the ActiveX Component:

  • Open up the properties of the TAL ActiveX component in whichever development environment you are using.
  • Scroll down until you see the GIFCompression property. Change that property to 'True'.
  • Scroll down until you see the LZWUnlockKey property. Change the value of that property to 29031947.

You can also set the properties in code using your development environment by using the following lines of code in one of your subroutines:


	TalBarCd1.GIFCompression = True
	TalBarCD1.LZWUnlockKey="29031947"

Categories: Tutorial / How-To

Last Updated: 2011.07.04

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