XnView Software

need to make a converter orf to bmp images and do not really know how to use this library, if you could help me with some tutorials

thank

Do you want to use XnView to convert images from orf to bmp or do you want to implement an orf to bmp converter based on the image library GFL?

I'm answering assuming that you want to use XnView to open and convert orf images:
According to the list of supported image format XnView can read orf files (Olympus RAW format). If you want to convert files, you simply have to download and install XnView and change the setting "Display all image file types". You will find this setting in the "XnView - Configuration wizard" which appears at first startup of XnView.
Alternatively, select menu "Tools > Options", category "General > Operations". Check the setting "Display all image file types" and you should be able to display your .orf files.

Notes:

• BMP doesn't compress image data well. For lossless saving/compression I recommend PNG. For lossy compression (with quality loss) JPG can be used for example.
• If you plan to convert many .orf files, the batch processing in XnView might be the right thing for you.

Related topic:
- Does XnView support graphic format .xyz?
- How to Batch convert several images at once