• vector image: eps
• raster images : Graphic Interchange Format (GIF), Joint Photographic Experts Group (JPEG), Portable Network Graphic (PNG), and Tagged Image File Format (TIFF).

Resolution:the number of pixels displayed per unit length format:

Recommended resolution

1. 300 dpi for color pictures
2. 300 to 600 dpi for black and white pictures
3. 600 to 900 dpi for combination art (photo and text)
4. 900 to 1,200 dpi for line art.

The standard figure size of most academic journals is about 86 mm (single column). The standard pixels per inch for line art is 900 to 1,200 ppi. Therefore, an image file of 900 ppi and 4 inches is of sufficient quality for most publications;