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.
PNG is a raster graphic data storage format that uses lossless compression algorithm to Deflate. PNG was created as a free format to replace GIF. PNG supports three main types of raster images: grayscale image, a color indexed image and the color image. PNG format stores graphical information in a compressed form.