File Formats

Page Layout Definition

Page Layout Definition

Page layout refers to the arrangement of text, images, and other objects on a page. The term was initially used in desktop publishing (DTP), but is now commonly used to describe the layout of webpages as well. Page layout techniques are used to customize the appearance of magazines, newspapers, books, websites, and other types of publications.

The page layout of a printed or electronic document encompasses all elements of the page. This includes the page margins, text blocks, images, object padding, and any grids or templates used to define positions of objects on the page. Page layout applications, such as Adobe InDesign and QuarkXpress, allow page designers to modify all of these elements for a printed publication. Web development programs, such as Adobe Dreamweaver and Microsoft Expression Studio allow Web developers to create similar page layouts designed specifically for the Web.

Since there are many applications that create customized page layouts, there is also a specific file format category for page layout file types. These files are similar to word processing documents, but may contain additional page formatting information and other types of visual content. You can view a list of Page Layout File Types at FileInfo.com.

File Formats

GIF Definition

GIF Definition

Stands for “Graphics Interchange Format.” GIF is an image file format commonly used for images on the web and sprites in software programs. Unlike the JPEG image format, GIFs uses lossless compression that does not degrade the quality of the image. However, GIFs store image data using indexed color, meaning a standard GIF image can include a maximum of 256 colors.

The original GIF format, also known as “GIF 87a,” was published by CompuServe in 1987. In 1989, CompuServe released an updated version of the format called “GIF 89a.” The 89a format is similar to the 87a specification, but includes support for transparent backgrounds and image metadata. Both formats support animations by allowing a stream of images to be stored in a single file. However, the 89a format also includes support for animation delays.

Even though the GIF format was published more than a quarter century ago, it is still widely used on the web. Nearly all GIFs use the 89a format. You can check the version of a specific GIF image by opening it in a text editor and looking at the first six characters listed in the document (GIF87a or GIF89a).

Since GIFs may only contain 256 colors, they are not ideal for storing digital photos, such as those captured with a digital camera. Even when using a custom color palette and applying dithering to smooth out the image, photos saved in the GIF format often look grainy and unrealistic. Therefore, the JPEG format, which supports millions of colors, is more commonly used for storing digital photos.

GIFs are better suited for buttons and banners on websites, since these types of images typically do not require a lot of colors. However, most web developers prefer to use the newer PNG format, since PNGs support a broader range of colors and include an alpha channel. (The alpha channel makes it possible for a single image with transparency to blend smoothly with any webpage background color.) Still, neither JPEGs nor PNGs support animations, so animated GIFs remain popular on the web.

NOTE: A GIF image can actually store more than 256 colors. This is accomplished by separating the image into multiple blocks, which each continue unique 256 color palettes. The blocks can be combined into a single rectangular image, which can theoretically produce a “true color” or 24-bit image. However, this method is rarely used because the resulting file size is much larger than a comparable .JPEG file.

How to pronounce “GIF”

According to Steve Wilhite, the creator of the original GIF format, it is pronounced “jiff” (like the peanut butter brand). However, most people still pronounce it “gif” (with a hard G). Therefore, either pronunciation is acceptable.

File extension: .GIF

File Formats

MP3 Definition

MP3 Definition

Stands for “MPEG Audio Layer-3.” MP3 is a compressed audio file format developed by the Moving Picture Experts Group (MPEG). A typical MP3 file sounds similar to the original recording, but requires significantly less disk space. MP3 files are often about one tenth the size of an uncompressed WAVE or AIFF file, which have the same audio quality as a CD.

The small file size and high fidelity of MP3 files helped popularize digital music downloads in the late 1990s and early 2000s. Instead of requiring a 40 megabyte download for a single song, the comparable MP3 file might be 4 MB. MP3s made it possible for users to download entire albums in roughly the same time it took to download a single WAV or AIFF file. For over a decade, MP3s were the most common way to store music files on computers and portable music players like the iPod.

While MP3s are still prevalent on the Internet, other file formats are now also used for audio compression. Advanced Audio Coding (AAC), for example, is used for songs on Apple’s iTunes Store. Ogg Vorbis is an open container format that is frequently used for royalty-free compression and streaming.

The MP3 File Format

An MP3 file includes a header, metadata, and compressed audio. The header includes information about the audio, such as the version of the encoding, the bitrate, and the (sample_rate|sample_rate). A high bitrate and sample rate produces better audio quality, but also a larger file size.

A common MP3 compression setting is a bitrate of 128 kbps and a sample rate of 44.1 kHz. This produces a file size of roughly one megabyte per minute.

MP3 metadata provides information about the actual recording. This data is usually saved in an ID3 tag, which is a standard format supported by most hardware and software media players. The bulk of the MP3 file contents is the actual compressed audio, which is stored as binary data.

File extension: .MP3

File Formats

MPEG Definition

MPEG Definition

Stands for “Moving Picture Experts Group.” MPEG is an organization that develops standards for encoding digital audio and video. It works with the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC) to ensure media compression standards are widely adopted and universally available.

The MPEG organization has produced a number of digital media standards since its inception in 1998. Examples include:

  • MPEG-1 – Audio/video standards designed for digital storage media (such as an MP3 file)
  • MPEG-2 – Standards for digital television and DVD video
  • MPEG-4 – Multimedia standards for the computers, mobile devices, and the web
  • MPEG-7 – Standards for the description and search of multimedia content
  • MPEG-MAR – A mixed reality and augmented reality reference model
  • MPEG-DASH – Standards that provide solutions for streaming multimedia data over HTTP (such as servers and CDNs)

Using MPEG compression, the file size of a multimedia file can be significantly reduced with little noticeable loss in quality. This makes transferring files over the Internet more efficient, which helps conserve Internet bandwidth. MPEG compression is so ubiquitous that the term “MPEG” is commonly used to refer to a video file saved in an MPEG file format rather than the organization itself. These files usually have a “.mpg” or “.mpeg” file extension.

File extensions: .MP3.MP4.M4V.MPG.MPE.MPEG

File Formats

Animated GIF Definition

Animated GIF Definition

An animated GIF is a GIF file that includes multiple images or “frames.” These frames are played back in sequence when the file is opened or displayed in a web browser. The result is an animated clip or a short movie.

The GIF file format includes a Graphics Control Extension (or “GCE block”), which enables a single GIF file to store multiple frames. This section also specifies the delay between frames, which can be used to set the frame rate or insert pauses at certain points within the animation. Another section, called the Netscape Application Block (NAB), specifies how many times the animation will repeat (a setting of “0” is used for infinite repetitions).

In the early years of the Web, animated GIFs were a popular way to display motion and liven up websites. They were commonly used for advertisements, such as banners and leaderboards. As Flash animations became more popular, animated GIFs became less prominent. However, animated GIFs have recently seen a resurgence on the web since they are supported by all platforms. For example, Apple’s iOS does not support Flash animations, but can display animated GIFs.

Several image editing programs, such as Adobe Photoshop and GIMP, can be used to create animated GIFs. Other graphics programs can merge multiple image files into a single GIF. Some video utilities can even convert short videos to animated GIFs. While this can be useful for sharing small videos on the web, the GIF format is not as efficient as the MPEG format for storing videos longer than a few seconds.

File Formats

PNG Definition

PNG Definition

PNG, which can be pronounced “ping” or “P-N-G,” is a compressed raster graphic format. It is commonly used on the Web and is also a popular choice for application graphics.

The PNG format was introduced in 1994, after the GIF and JPEG formats had already been around for several years. Therefore, PNG includes many of the benefits of both formats. For example, PNG images use lossless compression like GIF files, so they do not have any blurring or other artifacts that may appear in JPEG images. The PNG format also supports 24-bit color like the JPEG format, so a PNG image may include over 16 million colors. This is a significant difference between GIF and PNG, since GIF images can include a maximum of 256 colors.

Unlike the JPEG and GIF formats, the PNG format supports an alpha channel, or the “RGBA” color space. The alpha channel is added to the three standard color channels (red, green, and blue, or RGB) and provides 256 levels of transparency. JPEG images do not support transparent pixels and GIF images only support completely transparent (not partially opaque) pixels. Therefore, the PNG format allows Web developers and icon designers to fade an image to a transparent background rather than a specific color. A PNG with an alpha channel can be placed on any color background and maintain its original appearance, even around the edges.

While the PNG image format has many benefits, it is not suitable for all purposes. For example, digital photos are still usually saved as JPEGs, since PNGs take up far more disk space. GIFs are still used for animations since PNG images cannot be animated. Additionally, GIFs are still used on many websites since browsers only recently provided full support for the PNG format. However, now that most browsers and image editing programs support PNGs, it has become a popular file format for web developers and graphic artists.

File extension: .PNG

File Formats

Raster Graphic Definition

Raster Graphic Definition

Most images you see on your computer screen are raster graphics. Pictures found on the Web and photos you import from your digital camera are raster graphics. They are made up of grid of pixels, commonly referred to as a bitmap. The larger the image, the more disk space the image file will take up. For example, a 640 x 480 image requires information to be stored for 307,200 pixels, while a 3072 x 2048 image (from a 6.3 Megapixel digital camera) needs to store information for a whopping 6,291,456 pixels.

Since raster graphics need to store so much information, large bitmaps require large file sizes. Fortunately, there are several image compression algorithms that have been developed to help reduce these file sizes. JPEG and GIF are the most common compressed image formats on the Web, but several other types of image compression are available.

Raster graphics can typically be scaled down with no loss of quality, but enlarging a bitmap image causes it to look blocky and “pixelated.” For this reason, vector graphics are often used for certain images, such as company logos, which need to be scaled to different sizes.

File extensions: .BMP.TIF.GIF.JPG

File Formats

Vector Graphic Definition

Vector Graphic Definition

Unlike JPEGs, GIFs, and BMP images, vector graphics are not made up of a grid of pixels. Instead, vector graphics are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams. Paths are even used to define the characters of specific typefaces.

Because vector-based images are not made up of a specific number of dots, they can be scaled to a larger size and not lose any image quality. If you blow up a raster graphic, it will look blocky, or “pixelated.” When you blow up a vector graphic, the edges of each object within the graphic stay smooth and clean. This makes vector graphics ideal for logos, which can be small enough to appear on a business card, but can also be scaled to fill a billboard. Common types of vector graphics include Adobe Illustrator, Macromedia Freehand, and EPS files. Many Flash animations also use vector graphics, since they scale better and typically take up less space than bitmap images.

File extensions: .AI.EPS.SVG.DRW

File Formats

Bitmap Definition

Bitmap Definition

A bitmap (or raster graphic) is a digital image composed of a matrix of dots. When viewed at 100%, each dot corresponds to an individual pixel on a display. In a standard bitmap image, each dot can be assigned a different color. Together, these dots can be used to represent any type of rectangular picture.

There are several different bitmap file formats. The standard, uncompressed bitmap format is also known as the “BMP” format or the device independent bitmap (DIB) format. It includes a header, which defines the size of the image and the number of colors the image may contain, and a list of pixels with their corresponding colors. This simple, universal image format can be recognized on nearly all platforms, but is not very efficient, especially for large images.

Other bitmap image formats, such as JPEGGIF, and PNG, incorporate compression algorithms to reduce file size. Each format uses a different type of compression, but they all represent an image as a grid of pixels. Compressed bitmaps are significantly smaller than uncompressed BMP files and can be downloaded more quickly. Therefore, most images you see on the web are compressed bitmaps.

If you zoom into a bitmap image, regardless of the file format, it will look blocky because each dot will take up more than one pixel. Therefore, bitmap images will appear blurry if they are enlarged. Vector graphics, on the other hand, are composed of paths instead of dots, and can be scaled without reducing the quality of the image.

File extensions: .BMP.DIB