The Portable Network Graphics (.png) is a standard raster format. Because of compression, exporting to PNG can result in much smaller file sizes compared to other formats.
In the Export Map or Export Chart window, choose PNG (.png) from the Save as type list box.
Enter a value that represents the resolution produced by the display or printer in the DPI spin box.
The closer the match between the resolution of the file and the display or printer, the better the quality of the results.