Graphics Software Terminology
Last updated: May 11, 2007
Graphics jargon can be
confusing, especially
for those who are just learning how to edit digital photographs or work
with images for printing or
Web pages. There are countless
graphics software packages available, each with its own options and
even different names for the basic functions you can use to manipulate
images (also called
image
enhancement). To help you better grasp graphics software, we take a look at the genre and define the common
terminology to help you better maneuver your way
through the basics of working with your digital images.
Image Dimensions
Image dimensions are the length and width of your image, measured in
pixels. Some graphics programs will allow you to view and work with your
image in the equivalent inches or centimeters. Depending on what you
plan to use your image for, you may want to change the image size. For
example, if you are using a high-resolution digital photograph, you may
want to make the image smaller for publishing to a Web page. You will
have a couple choices: resize or resample.
Resize / Resample
When you resize or resample
an image, you're basically specifying a new pixel dimension (length and
width) for that image. The resize algorithm duplicates or
deletes pixels and if you choose resample it will smooth out edges and
fill in missing pixels with the appropriate color. Because of the
difference between resize and resample, it is generally best to use
resize on computer graphics and resample on more realistic photo images,
and images with more than 256 colors.
Color Depth
In computer graphics,
color depth is how you describe the range of
colors that can be used in an image. The more colors used in an image,
the more realistic it will look. Common values for color depth include the following:
256 colors; 16-bit, which is up to 65,000 colors; and 24-bit, which is
16,777,216 colors. Computer-generated graphics and clip art are best
suited to a lower color depth, while photos and realistic images are best
suited to 24 and 32-bit color depth. The more colors your image
contains, the larger the file size.
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Original
image (24-bit) showing zoom area |
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| (Zoomed
200x185 crop) 256 colors (8 bit) |
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| (Zoomed
200x185 crop) 16 colors (4 bit) |
Image Effects
Many graphics programs come with predefined algorithms that enable
you to add special effects to your images. The actual effects will
depend on the software you use. However, there are some standard ones
that you can expect to find in a good program. You can usually choose
different effects that will change the edges of your image, noise level,
gradient and other aspects of your image. With most programs you can
simply select the name of the image effect and the program will produce
the image with the effect, so you can save the image. You can also
choose "undo" if you don't like it and select another one to try. Also,
you may find your program offers an effects browser, which will open
your image as a thumbnail in a browser window that allows you to quickly
preview how each effect will look before performing the action. Image
effects are used as a way to change your image to add an artistic look,
make textured patterns, or produce an enhanced real-world view. Some
graphics programs will offer a few predefined effects, others designed
with effects in mind may offer hundreds of image effects to choose from.
The following examples show several common image effects.
Digital Photo Effects
With the popularity of
digital photography, many graphics programs now offer image effects
specifically for digital photos. These types of effects are used to
remove problems that can appear in your original digital photograph such
as various lens corrections (pincushion or fisheye) and red-eye removal
tools. Re-eye removal is becoming more of a standard photo effect in
graphics programs. Some options will simply auto-detect red-eye when you
run the function and remove it, while others provide more advanced
options by allowing you to place a circle over the red-eye area and
adjust the red-eye removal tool to your own liking. Others will provide
a selection of human and animal eyes that you can use to fill in the
red-eye on your own image.
Color Adjustments
Color adjustments can be used to change the overall tone of your image
and also to remove unwanted colors from your image as well. Color
adjustment changes usually affect an entire image, even if you have
selected only a small portion of the image to be adjusted. If you are
working with images that are 24-bit or higher you may be able to make
these changes to a specific part of the image. Color adjustments can
also take other colors from the image into consideration when running
the algorithm. For example if you add grey to a blue water scene, the
grey will be influenced by the blue. Color balance can also be used to
produce interesting image effects. By adding grey and yellow, for
example, you can produce a more aged or newspaper aged look to your
image.
One element of color adjustment that is
available in many graphics programs is color balance. This
function allows you to control the amount of red, green and blue in an
image. Other standard color adjustments found in many graphics program
allow you to adjust the brightness, contrast and gamma in the image.
These options are used to correct the brightness and contrast of
an image. Adjusting the brightness and contrast highlights midtones and
shadows to bring out detail in either light or dark areas. Gamma adjusts
the brightness and contrast in unison. Here are some examples of images
processed with several different color adjustment functions.
Removing Noise & Artifacts
In digital images
noise and
artifacts can often be a problem in images. Noise is used to
describe the occurrence of color dots or specks where there should be
none. For example, in a digital image of a pool of blue water, you may
notice white, grey or other colored specks in the image where it should
be blue. An artifact is used to describe any visible defect in the
image. "Jaggies",
stair-like lines that appear where there should be smooth straight lines
or curves are considered artifacts.
Again the preset options for artifact and
noise removal will differ among graphics programs, but good programs
will offer pre-defined options for small scratch removal, which is
useful when dealing with scanned images, noise removal with edge
preserving, salt and pepper removal (which removes extraneous black and
white dots), and also softening which will blur some noise in
photographs and give a softer tone to the image. Some programs will also
have a JPEG
artifact removal which helps remove artifacts introduced by the JPEG
compression algorithm.
Control Cursors (Tools)
Graphics programs offer a set of tools that you can use to make changes
and manipulate your images through cursor movement. The tools differ but
allow you to color or fill in areas of your image with user-selected
colors, crop out sections of an image, erase the
background,
or replace colors in an image. Here are some commonly used tools you
should become familiar with in your graphics program.
Crop
Using the crop function allows you to drag a rectangular shape
around an area in your image to cut off the sides to make it the
proper size or to remove unwanted parts. Most graphics applications
allow you to crop images with a clip feature.
Painting
The Painting tool changes the area of your image where you use the
cursor to add paint strokes to the image. You can use this tool to
fill in single pixels, add hard or soft lines, or select areas to
fill in with a solid color or, some programs will allow you to paint
with a texture rather than a single color.
Brush
A part of the Painting tool that that allows you to select a brush
shape (square, circle, oval and so on) and also the the thickness in
pixels you want to paint on your image with. As you move your cursor
over the image it leaves a stroke of color.
Dropper
The Dropper tool allows you to choose a foreground or background
color from your image to work with. If you had a specific blue in
your image that you wanted to use with the paint tool, for example,
you would use the dropper and click on one of the blue pixels to
change your foreground color.
Eraser
Eraser tools allow you to erase areas within your image to leave
behind transparency or a background color. There is also a
Background Eraser which provides more control in removing a
background to transparent.
Vangie 'Aurora' Beal -
Writer, www.Webopedia.com
Last updated: May 11, 2007
Optimizing Web Graphics 
Webreference.com article on how to
minimize file size and dithering for Web graphics. Includes sections on
the color palette, color reduction, compression, tools and techniques,
and several online references.
Corel Corporation home page
Corel's home page offers a search
utility for locating product information, links to news, company
information, a resource center, beta programs, conferences and tradeshow
information, and service and support information.
Computer graphics
resource page
Provides a categorized list of topics
(animation, desktop publishing, file formats, software, etc.) related to
computer graphics.
Adobe Systems home page
Adobe's home page offers links to their
popular line of desktop publishing products, including Photoshop,
PageMaker, FrameMaker, Illustrator, and PostScript. There are also links
to company news and information, support and services, free software,
and tips and techniques.
Photoshop tips page
Provides numerous tips on creating
graphics, images, and patterns with Adobe Photoshop.
Webopedia's "Did You Know... JPG vs. GIF vs. PNG"
This article discusses the three most commonly used graphics file
formats for putting graphics on the World Wide Web.
Webopedia's "Graphics File Formats"
This article discusses the most common types of graphics file formats
including TIFF, JPEG, GIF, and PNG.
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