Files with CMX extension are Corel Exchange image file format (also known as Corel Metafile Exchange) that is used as presentation by CorelSuite applications. It contains image data as vector graphics as well as metadata that describes the image. CMX files can be opened by CorelDraw, Corel Presentations, Paint Shop Pro and some versions of Adobe Illustrator. CMX files can be converted to other formats such as JPG and EPS.
PNG, Portable Network Graphics, refers to a type of raster image file format that use loseless compression. This file format was created as a replacement of Graphics Interchange Format (GIF) and has no copyright limitations. However, PNG file format does not support animations. PNG file format supports loseless image compression that makes it popular among its users. With the passage of time, PNG has evolved as one of the mostly used image file format.
You can also convert CMX into many other file formats. Please see the complete list below.