G and H of Digital Media - Google and Hard Drive
Podcast - Edition Two - Google
GIF File
The Graphical Interchange Format (GIF) is one of the most widely used image formats on the web. GIF files are recognizable by their .gif file extension. GIF is suitable for images with sharp edges and relatively few gradations of color, such as line art, cartoons, and text. You can also create background transparencies and animations using GIF images.
History of GIF
In 1987, CompuServe Corporation created the GIF file format to be used for the storage and online retrieval of bitmapped graphical data. The GIF specification required the use of the LZW algorithm to compress the data stored in each GIF file. In 1984, while working for Sperry Corporation (now Unisys), Terry Welch modified the Lempel-Ziv 78 (LZ78) compression algorithm for greater efficiency for implementation in high-performance disk controllers. The result was the LZW algorithm.
Although GIF itself was released as a free and open specification, Unisys maintained a patent for LZW compression in some countries until summer 2004. (These patents have expired; Unisys now holds and has patents pending on improvements to LZW compression.) In the 1990s (before the LZW US patent expired), developers concerned about patent enforcement devised the PNG format, intended as a patent-free replacement for GIF.
Gaussian blur, named for Carl Friedrich Gauss, describes blurring an image by a Gaussian function. It is a widely used effect in graphics software, typically to reduce image noise and reduce detail. The visual effect of this blurring technique is a smooth blur resembling that of viewing the image through a translucent screen, distinctly different from the bokeh effect produced by an out-of-focus lens or the shadow of an object under usual illumination. Gaussian smoothing is also used as a pre-processing stage in computer vision algorithms in order to enhance image structures at different scales—see scale-space representation and scale-space implementation.
Mathematically, applying a Gaussian blur to an image is the same as convolving the image with a Gaussian function; this is also known as a two-dimensional Weierstrass transform. By contrast, convolving by a circle (i.e., a circular box blur) would more accurately reproduce the bokeh effect. Since the Fourier transform of a Gaussian is another Gaussian, applying a Gaussian blur has the effect of reducing the image’s high-frequency components; a Gaussian blur is thus a low pass filter.
Grayscale is a range of shades of gray without apparent color. The darkest possible shade is black, which is the total absence of transmitted or reflected light. The lightest possible shade is white, the total transmission or reflection of light at all visible wavelength s. Intermediate shades of gray are represented by equal brightness levels of the three primary colors (red, green and blue) for transmitted light, or equal amounts of the three primary pigments (cyan, magenta and yellow) for reflected light.
In the case of transmitted light (for example, the image on a computer display), the brightness levels of the red (R), green (G) and blue (B) components are each represented as a number from decimal 0 to 255, or binary 00000000 to 11111111. For every pixel in a red-green-blue ( RGB ) grayscale image, R = G = B. The lightness of the gray is directly proportional to the number representing the brightness levels of the primary colors. Black is represented by R = G = B = 0 or R = G = B = 00000000, and white is represented by R = G = B = 255 or R = G = B = 11111111. Because there are 8 bit s in the binary representation of the gray level, this imaging method is called 8-bit grayscale.
In the case of reflected light (for example, in a printed image), the levels of cyan (C), magenta (M), and yellow (Y) for each pixel are represented as a percentage from 0 to 100. For each pixel in a cyan-magenta-yellow (CMY) grayscale image, all three primary pigments are present in equal amounts. That is, C = M = Y. The lightness of the gray is inversely proportional to the number representing the amounts of each pigment. White is thus represented by C = M = Y = 0, and black is represented by C = M = Y = 100.
In some systems that use the RGB color model, there are 2 16 , or 65,636, possible levels for each primary color. When R = G = B in this system, the image is known as 16-bit grayscale because the decimal number 65,536 is equivalent to the 16-digit binary number 1111111111111111. As with 8-bit grayscale, the lightness of the gray is directly proportional to the number representing the brightness levels of the primary colors. As one might expect, a 16-bit digital grayscale image consumes far more memory or storage than the same image, with the same physical dimensions, rendered in 8-bit digital grayscale.
In analog practice, grayscale imaging is sometimes called “black and white,” but technically this is a misnomer. In true black and white, also known as halftone, the only possible shades are pure black and pure white. The illusion of gray shading in a halftone image is obtained by rendering the image as a grid of black dots on a white background (or vice-versa), with the sizes of the individual dots determining the apparent lightness of the gray in their vicinity. The halftone technique is commonly used for printing photographs in newspapers.
In some cases, rather than using the RGB or CMY color models to define grayscale, three other parameters are defined. These are hue, saturation and brightness . In a grayscale image, the hue (apparent color shade) and saturation (apparent color intensity) of each pixel is equal to 0. The lightness (apparent brightness) is the only parameter of a pixel that can vary. Lightness can range from a minimum of 0 (black) to 100 (white).
A gigabyte (GB) is a measure of computer data storage capacity and is “roughly” a billion bytes. A gigabyte is two to the 30th power, or 1,073,741,824 in decimal notation. The term is pronounced with two hard Gs. The prefix, “giga” comes from a Greek word meaning “giant.”
HTML
(This is my favourite webpage www.imdb.com’s HTML source as an example)
HTML is a computer language devised to allow website creation. These websites can then be viewed by anyone else connected to the Internet. It is relatively easy to learn, with the basics being accessible to most people in one sitting; and quite powerful in what it allows you to create. It is constantly undergoing revision and evolution to meet the demands and requirements of the growing Internet audience under the direction of the » W3C, the organisation charged with designing and maintaining the language.
The definition of HTML is HyperText Markup Language.
- HyperText is the method by which you move around on the web — by clicking on special text called hyperlinks which bring you to the next page. The fact that it is hyper just means it is not linear — i.e. you can go to any place on the Internet whenever you want by clicking on links — there is no set order to do things in.
- Markup is what HTML tags do to the text inside them. They mark it as a certain type of text (italicised text, for example).
HTML is a Language, as it has code-words and syntax like any other language.
Hyperlink (info from www.wisegeek.com)
A hyperlink is a graphic or a piece of text in an Internet document that can connect readers to another webpage, or another portion of a document. Web users will usually find at least one hyperlink on every webpage. The most simple form of these is called embedded text or an embedded link.
In this instance, a hyperlink will show up as a single word or group of words that will usually be marked as underlined, and are frequently blue in color. Clicking on the hyperlink may take one to another part of the page, or it may open another Internet page.
The HTML code for a hyperlink is relatively simple. It looks like this: wiseGEEK which will display display like this: wiseGEEK. Clicking on this hyperlink will take send the web surfer to wiseGEEK’s homepage. The code is easy to duplicate. It always begins as , then the word that serves as the hyperlink and finally, .
A more complicated link can take one to a specific place in a document. It can either be text or graphic. It may also be a blank area on a screen that performs functions when one clicks on it. There are numerous uses for the hyperlink, and constantly more being discovered.
Helper Applications
A helper application is an external viewer program launched to display content retrieved using a web browser. Some common examples include Windows Media Player and QuickTime Player for playing streaming content.
Unlike a plugin (whose full code is included into browser code), a small line is added to the browser code to tell it to open a certain helper application in case it encounters a certain file format.
Halo Effect (also from www.wisegeek.com)
Halo effects are psychological tendencies studied in some detail by the field of cognitive psychology. They occur when one good quality about a person, say, they’re a fan of the same sports team - leads us to over-attribute good qualities to them in other areas. In a school context, students that get an “A” on the first piece of homework they turn in might end up getting undue slack from a teacher on further grading, because the teacher expects them to continue producing A-quality work. The inverse of the halo effect is the “devil effect” or the “horns effect,” where one instance of bad performance causes the victim to be attributed negatively in an unfair fashion in the future.
The halo effect is a cognitive bias, one among hundreds, a “mental shortcut” or even “cognitive illusion” that causes people to behave in ways that an unbiased observer empirically and systematically considers unjustified. Because our entire lives are permeated by these cognitive judgments, studies of biases like the halo effect go down to the very fabric that underlies our society.
In one famous study, commanding officers were asked to rate their soldiers on an array of traits, both good and bad. Analysis of the results showed that positive and negative qualities were strongly correlated with one another. This shows that people tend to paint others with a broad brush - “good in general” or “bad in general.” These attributions are made early, sometimes in the first few seconds of meeting someone (hence the piece of wisdom that says first impressions are so important), creating anchoring effects days, weeks, or even years after the fact. Halo effects are a serious problem in recruiting for Human Resources departments, where studies have shown time and time again that past behavior is a way better predictor of future behavior that interviewer impressions.
In professional auto shows, halo cars are super-nice cars that are put on display so that the awe elicited by them leaks over into the whole show. We see this effect not just in car shows but in organizations, museums, universities, governments, and so on. The province of Alberta, in Canada, has even gone so far as to pay leading scientists $20 million US Dollars (USD) to move to their area and perform research there for the next 10 years. Clearly not all of these scientists will produce results for the province worth over $20 million USD, so the only alternative explanation is that government officials are trying to produce a halo effect around their province and cities, to attract promising young researchers.
The halo effect is deep and omnipresent. Every one of us likely falls prey to it everyday. Examine your own thought processes consciously, and you’ll see that halo effects permeate practically every judgment you make - including your judgment of the quality of this website and the humble author of this article.
H.264 video
H.264 is a standard for video compression. It is also known as MPEG-4 Part 10, or MPEG-4 AVC (for Advanced Video Coding). It is one of the latest block-oriented motion-estimation-based codecs developed by the ITU-T Video Coding Experts Group (VCEG) together with the ISO/IEC Moving Picture Experts Group (MPEG) as the product of a partnership effort known as the Joint Video Team (JVT). The ITU-T H.264 standard and the ISO/IEC MPEG-4 Part 10 standard (formally, ISO/IEC 14496-10) are jointly maintained so that they have identical technical content. The final drafting work on the first version of the standard was completed in May 2003.
Hard Drive
The mechanism that reads and writes data on a hard disk. Hard disk drives (HDDs) for PCs generally have seek times of about 12 milliseconds or less. Many disk drives improve their performance through a technique called caching.
There are several interface standards for passing data between a hard disk and a computer. The most common are IDE and SCSI.
Hard disk drives are sometimes called Winchester drives, Winchester being the name of one of the first popular hard disk drive technologies developed by IBM in 1973.
Histogram
This histogram depicts digital photography
A bar graph of a frequency distribution in which the widths of the bars are proportional to the classes into which the variable has been divided and the heights of the bars are proportional to the class frequencies.
Hue
Hue is one of the three main attributes of perceived color, in addition to lightness and chroma (or colorfulness). Hue is also one of the three dimensions in some colorspaces along with saturation, and brightness (also known as lightness or value). Hue is that aspect of a color described with names such as “red”, “yellow”, etc.
Usually, colors with the same hue are distinguished with adjectives referring to their lightness and/or chroma, such as with “light blue”, “pastel blue”, “vivid blue”. Notable exceptions include brown, which is a dark orange,[1] and pink, a light red with reduced chroma.
In painting color theory, a hue refers to a pure color—one without tint or shade (added white or black pigment, respectively). A hue is an element of the color wheel.
Hostname
A hostname (occasionally also, a sitename) is the unique name by which a network-attached device (which could consist of a computer, file server, network storage device, fax machine, copier, cable modem, etc.) is known on a network. The hostname is used to identify a particular host in various forms of electronic communication such as the World Wide Web, e-mail or Usenet.
On the Internet, the terms “hostname” and “domain name” are often used interchangeably, but there are subtle technical differences between them.