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Chapter 7
Graphic files can be either of the following types:
Types of Graphic Files
Keep the following guidelines in mind:
If you are working with Adobe Photoshop:
Adobe Photoshop
Considerations
In order to make bit-mapped EPS files work efficiently, keep their size and resolution as
Working with
Bit-Mapped EPS
small as possible. For example, a 30x50 pixel image at a 72 dpi (dots per inch) resolution
processes very quickly. A full-screen image at the same resolution can take considerably
longer to process and display. The image's complexity ultimately determines its process-
ing speed.
For example, suppose you have a 300 dpi image that measures 4x5 inches. Such an image
contains approximately 2 million pixels! A standard video monitor has less than 400,000
pixels available. If you import the image into PowerScript and then scale it to fit the
screen, the image might look satisfactory, but processing time would be lengthy and
wasteful because you are forcing PowerScript to process more pixels than the screen can
actually display.
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•
Bit-mapped (pixel-based, or paint) images consist of individual dots, or screen pix-
els. You can create these types of files using paint and image processing programs,
such as Adobe Photoshop.
•
Vector-based (draw-type, or object-based) images consist of lines, shapes, arcs, and
paths. You can create these types of files with illustration and drawing programs
such as Adobe Illustrator, CorelDRAW, Macromedia FreeHand, and others.
•
When creating files that consist of a dozen or fewer objects, it is usually best to cre-
ate these as vector-based files.
•
Images larger than 200 x 300 pixels should normally be vector-based images.
•
Images smaller than 100 x 100 pixels are best done as bit-mapped images, unless
they are relatively simple (that is, contain only a couple of objects).
•
For bit-mapped images with few colors or significant flat areas, save them in the
GIF format.
•
For bit-mapped images with many colors, gradations, or patterns, JPEG is normally
the most efficient format.
•
When you require transparency, use the EPS or APS format.
•
Work in RGB mode. If a file is not RGB mode, convert it before saving.
•
Save the file as a "Photoshop EPS."
•
Do not include a preview of the image.
•
Use JPEG-Low Quality encoding when the option is available.
The JPEG-Low Quality setting greatly compresses the file at some loss in image
quality. It is unlikely you will notice much difference on your monitor. If you are
not satisfied with the quality, save the file at a higher JPEG setting.
•
Turn off DCS, if the option is available.
•
Do not include a clipping path, halftone screen, or transfer functions.
•
It is very important to downsample the image to 72-dpi at the desired size before
saving to reduce file size. Remember that the video screen contains only 720 x 485
pixels (NTSC) or 720 x 576 pixels (PAL).
Advanced PowerScript Functions
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