Art 86 - Digital Illustration
Glossary of Terms
Raster Graphics: digital images created or captured (by scanning) as a set of samples of a given space. A raster is a grid of x and y coordinates on a display space. A raster image file identifies which of these coordinates to illuminate in monochrome or color values. The raster file is sometimes referred to as a bitmap because it contains information that is directly mapped to the display grid. A raster file is usually larger than a vector graphics image file.
Vector Graphics: the creation of digital images through a sequence of commands or mathematical statements that place lines and shapes in a given two-dimensional or three-dimensional space. In physics, a vector is a representation of both a quantity and a direction at the same time. In vector graphics, the file that results from a graphic artist's work is created and saved as a sequence of vector statements. For example, instead of containing a bit in the file for each bit of a line drawing, a vector graphic file describes a series of points to be connected. One result is a much smaller file.
Pixel (Picture Element): a pixel is a tiny dot of light on the monitor. It is the smallest part of every image you see on the monitor. The color of a pixel is partly determined by how many bits (on/off units) are used to store the pixel.
Bit (Binary Digit): a bit is an electronic signal, which is either on (1) or off (0). It is the smallest unit of information the computer uses. Computers use the binary system to work with data. All data is stored in binary code as 1's and 0's (bits). A bit might be called the "on/off" unit of information.
Byte: byte is a group of 8 bits, strung together. Each byte (8 bits) means something to the computer. The byte "01000001" means the capital letter A. The byte "01000010" means the capital letter B. bytes are arranged in units of K, MB, GB (kilobyte = 1000 bytes, megabyte = 1 million bytes, gigabyte = 1 billion bytes)
Files and Formats
A file is an entity of data available to users (including the system itself and its application programs) that is capable of being manipulated as a unit. The file must have a unique name within its own directory. Files with given formats are described by giving them a particular file name suffix (file name extension.) In general, the suffixes tend to be as descriptive of the formats as they can within the limits of the number of characters allowed for suffixes by the operating system. Conventionally, the extension is separated by a period from the name and contains three or four letters that identify the format.
A file format is the layout of a file in terms of how the data is organized. A program that uses a file must be able to recognize and possibly access data within the file. For example, the program that we call a Web browser is able to process and display a file in the HTML format so that it appears as a Web page, but it cannot display a Microsoft's Excel file. A program that uses or recognizes a particular file format may or may not care whether the file has the appropriate extension name since it can actually examine the bits in the file to see whether the format (layout) is one it recognizes. There are as many different file formats as there are different programs to process the files.
Most programs can create different file formats, including Illustrator. Many file formats use compression to reduce the file size. Lossless techniques compress the file without loosing any information; lossy techniques remove detail and lower image quality. Illustrator has four basic file formats—AI, PDF, EPS, and SVG. These formats are called native formats because they can preserve all Illustrator data. You can also export artwork in a variety of file formats for use outside of Illustrator. These formats are called non-native formats because Illustrator will not be able to retrieve all of the data if you reopen the file in Illustrator.
AI (Adobe Illustrator) is the native Illustrator file format. Used to save original editable files for backup and archiving. All your work should be save in this format always!
PDF (Portable Document Format) is a cross-platform, cross-application file format. PDF files accurately display and preserve fonts, page layouts, and both vector and bitmap graphics. In addition, PDF files can contain electronic document search and navigation features such as electronic links.
EPS (Encapsulated PostScript) file format can contain both vector and bitmap graphics and is supported by most graphics programs. EPS format is used to transfer PostScript artwork between applications.
SVG is a vector format that produces high-quality, interactive web graphics. There are two versions of the SVG formats: SVG and Compressed SVG (SVGZ). SVGZ can reduce file sizes by 50% to 80%; however, you cannot edit SVGZ files using a text editor.
BMP A standard Windows image format. You can specify a color model, resolution, and anti-alias setting for rasterizing the artwork, as well as a format (Windows or OS/2) and a bit depth to determine the total number of colors (or shades of gray).
EMF (Enhanced Metafile) Widely used by Windows applications as an interchange format for exporting vector graphics data. Illustrator may rasterize some vector data when exporting artwork to EMF format
JPEG (Joint Photographic Experts Group) a term for image files produced by using a JPEG standard, using a range of compression algorithms. The highest quality results in the largest file, you can make a trade-off between image quality and file size.
PICT is a Mac OS image file format for graphics and page-layout applications. Used as an intermediary file format for transferring images between applications. PICT format is especially effective for compressing images with large areas of solid color.
SWF (Flash) A vector-based graphics format for interactive, animated web graphics for use in web design, and viewable in any browser equipped with the Flash Player plug‑in.
PSD (Photoshop) The standard Photoshop format. If your artwork contains data that cannot be exported to Photoshop format, Illustrator preserves the appearance of the artwork by merging the layers in the document or by rasterizing the artwork.
GIF (Graphics Interchange Format) is one of the two most common file formats for graphic images on the World Wide Web. The LZW compression algorithm used in the GIF format is owned by Unisys, and companies that make products that exploit the algorithm need to license its use from Unisys.
PNG (Portable Network Graphics format) Used for lossless compression and for display of images on the web. Unlike GIF, PNG supports 24‑bit images and produces background transparency without jagged edges; however, some web browsers do not support PNG images.
TGA (Targa) Designed for use on systems that use the Truevision® video board.
TXT (Text Format) Used to export text in an illustration to a text file.
TIFF (Tagged-Image File Format) Used to exchange files between applications and computer platforms. TIFF is a flexible bitmap image format supported by most paint, image-editing, and page-layout applications. Most desktop scanners produce TIFF files.
WMF (Windows Metafile) An intermediate exchange format for 16‑bit Windows applications. WMF format is supported by almost all Windows drawing and layout programs. However, it has limited vector graphics support.