The format has a TIFF-image structure. It is generated by Canon cameras. The CR2 photo is stored in an uncompressed form and allows you to edit such settings as white balance, exposure, and other settings for photos that were already taken. It is the successor format to CRW, which was used in previous generation Canon SLR cameras.
This format was developed by Apple for storing vector and bitmap images with metadata. It was the main format for the QuickDraw graphics software. PCT supports 32-bit and 24-bit images. At the moment, the format is obsolete and has been superseded by more functional solutions.