The following list and table show specifications and requirements for Mac OS X application screenshots:
File Type: High-quality JPEG, TIFF, or PNG in the RGB color space
Quality: 72dpi, RGB, flattened
Transparency: Not allowed
Required: At least one screenshot is required and up to four additional screenshots are permitted
Type
Dimensions (px)
Notes
1280 x 800
16:10 aspect ratio
1440 x 900
16:10 aspect ratio
2880 x 1800
16:10 aspect ratio