Above: JPEG for the Web image.
JPEG, TIFF, GIF, PNG PDF, EPS Formats
by Ginger Rosenkrans
GIF: Graphics Interchange
Format. It's pronounced with a hard "g." Invented by Compuserve for use on computer networks, GIF is the
prevalent graphics format for images on the Internet. GIF Images use a fixed color palette (limited to only 256
colors - not the full spectrum of colors available to your monitor). The GIF
format uses compression for smaller files and faster downloads. This format is
best for images with solid colors or areas of uniform color such as
illustrations and logos. Save vector images for the
web as GIF files.
PNG:
Portable
Network Graphics. It's
pronounced like "ping" as in ping pong. The PNG
format was developed by an Internet committee expressly to be patent-free. It
provides a number of improvements over the GIF format but not intended to
replace the JPEG format. A PNG file is
compressed in lossless fashion (lossless: all image information is restored when
the file is decompressed during viewing). You can control the degree of opacity
in an image with a PNG file format.
JPEG: Joint Photographic
Experts Group. It's pronounced like "Jay-Peg." An ISO (International Standards Organization) body creating a
new standard for digitizing still photographic images. The standard (which is
also called JPEG) is cooperatively developed. Unlike GIF files, the JPEG format can take advantage of the full
spectrum of colors available to your monitor. Best to save as photos/raster
images as JPEG for Web
pages. The JPEG format also uses compression for smaller files and faster
downloads. However, unlike the compression method used in GIF files, the JPEG
compression is "lossy" which means it discards data in the process.
Once a file is saved in JPEG format the data is permanently lost. If you want
all the image data available for future use, save the image using no compression
or "lossless" compression and make JPEG copies from it.
TIFF: Tagged Image File Format. A standard graphics file format that
can be used to store grayscale and color images. TIFF makes files smaller.
Used for bitmaps. The TIFF format is supported by virtually all graphics
applications. Save as TIFF for printed documents.
EPS:
Encapsulated PostScript® - A file format used for both vector
graphics and bitmaps. EPS files contain a PostScript description of the graphic
data within them. EPS files are unique in that you can use them for vector
graphics, bitmap images, type or even entire pages.
PDF: Adobe® Portable Document Format
The Adobe Portable Document
Format (PDF) is used for publishing electronic documents to be distributed over
the Internet and other online services. The advantages to PDF files are:
1. Their compact size, which.makes them ideal for distributing product brochures
and technical manuals over the Internet.
2. They are platform independent -- they work with both Mac® and PC computers.
3. The software used to read and print them is free.
4. They display and print using the PostScript® page-description language. That
means if line art is embedded as vector objects, it will display and print
perfectly at any size or resolution. Plus it can be extracted and placed into
illustration documents or bitmap images.
5. Fonts are embedded within them so the target computer does not have to have
the fonts installed to view them.
6. They are fully searchable.
7. They can contain hyperlinks to pages within the PDF document itself or to a
web page on the Internet - or to movie clips.
8. They contain PostScript® data and can be imported into both image editors
and illustration programs just like EPS files.
9. Vector art contained in the PDF file will make Perfect printed output at any
resolution -- just as if the output were being printed from a job saved as a
PostScript .PS or .PRN file. If there are embedded bitmaps they will usually be
downsampled to 72 pixels per inch for viewing on a monitor or for transporting
over the Internet. This is to keep their file size small. However, bitmaps can
be embedded at high resolution for high-end output. To view PDF files over the
Internet , you must have the Adobe Acrobat reader. It’s free. Go to Adobe’s
Web site at http://www.adobe.com
To create or write PDF files, you must purchase Adobe Acrobat. Go to
Adobe’s Web site for more information.
Saving in TIFF, EPS, PDF, JPEG,
GIF:
For printed publications/documents:
generally, save files as TIFF, EPS, or PDF. Some places will want a JPEG.
For Web: save files as JPEG if it’s a photo and save as GIF if it’s a
flat illustration or text with color backgrounds!! You can save as PDF if
you’re publishing
electronic documents to be distributed over the Internet and other online
services
Note: GIF is flat imaging (e.g., type)
JPEG is more for photos, artwork that resembles paintings—there’s more
color information—256 to millions of color in JPEG
PNG: save raster images (like photos) that
have transparencyopacity for the web.
Note: In Photoshop, be sure to merge liked layers. This will flatten.
Flattening your image eliminates all layers and places all of the content onto
one background. Flatten only for print
and not Web!! When publishing photos on the Web, be sure to compress them using
programs like Photoshop. In Photoshop, save your photos for the Web by:
File>Save for the Web
EPS
If the graphics application you are using cannot read
native vector files the next best thing would be to save them as EPS
(Encapsulated PostScript) files. These are self-contained PostScript files that
contain the same mathematical descriptions as the vector files they are made
from. Even bitmaps can be saved in the EPS file format. EPS files are supported
by most all graphics applications. It is the most portable format for this
reason. It is best to use EPS files for all line art and illustrations because
they can be reproduced at any size or resolution and still display exactly as
they were drawn. Use them wherever native vector files cannot be used.
|
