The RLB extension is attached to bitmap images created using software by Wavefront Technologies. The latter was a company specialized in animation software and became part of Silicon Graphics in mid-1990s. The RLB format is currently considered uncommon and obsolete.
The quick and simple way to handle your files is to get a quality piece of software, such as reaConverter. This software is extremely efficient in managing a wide range of batch conversions. As you will soon realize, reaConverter will help you avoid spending countless hours trying to figure out how to convert multiple RLB files as once.
JPEG JPG PNG GIF TIFF TIF BMP ICO EMF WMF AI PDF EPS PS EPI WEBP WEBPLL JP2 PCX TGA DWG DWF DXF DGN WMZ CGM DRW SHP GBR PCT MIF PLT PCL SVG WPG CIN DCX DIS HRU MTV PRC RAD PIC RLA QRT SGI XBM XPM SWF CAL FAX FITS PSD PGM JXR BPG APNG DDS SVGZ CG4 FLIF AVIF