Adobe InDesign CS3 - Manual (Page 342)

INDESIGN CS3
User Guide
335
Graphics Interchange Format (.gif) files
Graphics Interchange Format (GIF) is a standard for displaying graphics on the World Wide Web and other online
services. Because it compresses image data without losing detail, its compression method is called lossless. Such
compression works well with graphics that use a limited number of solid colors such as logos and charts; however,
GIF cannot display more than 256 colors. For this reason it is less effective for displaying photographs online (use
JPEG instead) and is not recommended for commercial printing. If an imported GIF file contains transparency, the
graphic interacts only where the background is transparent.
JPEG (.jpg) files
The Joint Photographic Experts Group (JPEG) format is commonly used to display photographs and other
continuous-tone images in HTML files over the web and in other online media. The JPEG format supports CMYK,
RGB, and grayscale color modes. Unlike GIF, JPEG retains all of the color information in an RGB image.
JPEG uses an adjustable, lossy compression scheme that effectively reduces file size by identifying and discarding
extra data not essential to the display of the image. A higher level of compression results in lower image quality; a
lower level of compression results in better image quality, but a larger file size. In most cases, compressing an image
using the Maximum quality option produces a result that is indistinguishable from the original. Opening a JPEG
image automatically decompresses it.
Note: JPEG encoding, which can be performed on an EPS or DCS file in an image-editing application such as Photoshop,
does not create a JPEG file. Instead, it compresses the file using the JPEG compression scheme explained above.
JPEG works well for photographs, but solid-color JPEG images (images that contain large expanses of one color) tend
to lose sharpness. InDesign recognizes and supports clipping paths in JPEG files created in Photoshop. JPEG can be
used for both online and commercially printed documents; work with your prepress service provider to preserve
JPEG quality in printing.
See also
“Export to JPEG format” on page 104
Bitmap (.bmp) files
BMP is the standard Windows bitmap image format on DOS and Windows-compatible computers. However, BMP
does not support CMYK, and its color support is limited to 1, 4, 8, or 24 bits. It is less than ideal for commercially
printed or online documents, and it is not supported by some web browsers. BMP graphics can provide acceptable
quality when printed on low-resolution or non-PostScript printers.
See also
“Import options for graphics” on page 340
Encapsulated PostScript (.eps) files
The Encapsulated PostScript (EPS) file format is used to transfer PostScript language artwork between applications,
and is supported by most illustration and page-layout programs. Typically, EPS files represent single illustrations or
tables that are placed into your layout, but an EPS file can also represent a complete page.