Visual Basic 6: Tif Page convert from compression type ZLW, JPEG etc to Group4

Question

Hi,

Does anyone know of an open source library in Visual Basic 6 that converts pages in a TIF file from lets say LZW to Group4 format?

Thanks.

Answer 1

An edit of my answer to your other question!

ImageMagick is an excellent free open source image manipulation package. There is an OLE (ActiveX) control which you could use from VB6. I've never tried it myself - I always use the ImageMagick command line. I understand the control just takes the normal command lines anyway.

The command-line element for changing the TIFF format would be -compress. Something like this below to write in Group4 format (air code based on tutorial and manual)

convert myfile.tiff -compress Group4 myGroup4file.tiff

Choices for the -compress argument qualifier include: None, Group4, and LZW.

EDIT: ImageMagick is licensed under the GPL: if you use the control and redistribute your program, it's possible your program would have to be free open-source. Apparently it's not yet been legally tested whether dynamic linking to a GPL library or control invokes the GPL. You could always launch the ImageMagick command-line which to me should be safe [I am not a lawyer].

EDIT2: The ImageMagick website says it uses GPL but the license wording doesn't look like GPL 1 2 or 3 to me. It also contains this "For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof"

Answer 2

Look, the thing says it is GPL you need to respect that. These people are volunteering their time in good faith. Don't try to screw them over by trying to weasel out of the license. It is abusive and it is not legal. Simply using the command line interface through a system call is enough to trigger the GPL if you distribute the combined works as a single & seamless processing entity. If your program can work without it being installed it's not a derivative work. i.e. it has to remain an optional plugin.

Answer 3

The FreeImage library has worked well for me in the past.

http://freeimage.sourceforge.net/