Digital Graphics Article
Pixels
Pixel (Picture Element)- Pixels are dots used to display an image on a screen or printed matter. A pixel usually consists of ratio between three component colours. Red, Green and Blue (RGB). The RGB colour model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors. The best way to describe it is with a picture. On color monitors, each pixel is actually composed of three dots - a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy and unclear.
If an image is made up of a large amount of pixels e.g 720x480 pixels, then the image will be a good quality. However if there are less pixels used in the image then it will be of poorer quality in comparison the an image with 720 pixels by 420 pixels. However, when an image is stretched or enlarged, some of the image quality will be lost and you will start to see the individual pixels the more you manipulate the images.
Bitrate
The bitrate of a pixel, determines how many different colours can be used by each pixel of the picture, therefore it determines how detailed the picture is. The lower the bitrate is (for example 8bit), then the lower the image quality is because there aren’t as many colours. When the bitrate is high (24bit) then you will notice a much more detailed image as there is more colours to use to make up the image.
Resolution
Is sometimes identified by the width and height of the image as well as the total number of pixels in the image. This would normally be shown by writing the number of pixels down the side, by the number of pixels along the top. For example 640 by 480.
Sometimes the resolution of an image depends on whereat is being output (e.g web). If it was to be output
Raster/Bitmap Images.
A raster image, also called a bitmap, is a way to represent digital images. The raster image takes a wide variety of formats, including the familiar .gif, .jpg, and .bmp. A raster image represents an image in a series of bits of information, which translate into pixels on the screen. These pixels form points of colour, which create an overall finished image.
.bmp- The bmp file format, also known as bitmap image file, is generally used to store bitmap digital images. However the .bmp file format is also capable of storing 2D digital images of arbitrary width, height, and resolution, both monochrome and color, in various color depths, and optionally with data compression, alpha channels, and color profiles. It can use different bitrates, ranging all the way up to 32bit.
.jpg- In computing, the .jpg file format is a commonly used method of lossy compression for digital images. The JPEG compression algorithm is at its best on photographs and paintings of realistic scenes with smooth variations of tone and color. For web usage, where the amount of data used for an image is important, JPEG is very popular. JPEG is also the most common format saved by digital cameras.
.png- Portable Network Graphics is a bitmapped image format that employs lossless data compression. PNG was created to improve upon and replace GIF (Graphics Interchange Format) as an image-file format not requiring a patent license. PNG was designed for transferring images on the Internet, not for professional-quality print graphics, and therefore does not support non-RGB color spaces such as CMYK.
.gif- The Graphics Interchange Format is a bitmap image format that was introduced by CompuServe in 1987 and has since come into widespread usage on the World Wide Web due to its wide support and portability.
.tiff- Tagged image file format is a file format for storing images, popular among graphic artists, the publishing industry, and both amateur and professional photographers in general. As of 2009, it is under the control of Adobe Systems. Originally created by the company Aldus for use with what was then called "desktop publishing", the TIFF format is widely supported by image-manipulation applications
Lossy compression- Lossy raster compression is where a specific piece of data is compressed by losing some of the original file. The pieces of data that are removed from the file are not very important so therefore you cannot really tell that they have been discarded from the file.
Lossless Compression- A lossless compression is where every single piece of data that was originally in the file remains after the file is uncompressed. All of the information is completely the same.
Vector Graphics-
Is the use of geometry such as points, lines, curves, and shapes or polygons, which are all based on mathematical expressions, to represent images in computer graphics. "Vector", in this context, implies more than a straight line. The other way of representing graphical images is through bit-maps in which the image is made up of a pattern of dots (note that bit-maps are often referred to as raster graphics). Programs that allow you to create and manipulate vector graphics are called draw programs and programs that manipulate bit-map images are called paint programs. Vector graphics are more flexible than bit-maps because they can be easily re-sized. In addition, images stored as vectors look better when displayed on high-resolution printers and monitors. Bit-map images look the same, regardless of the resolution of the display. Another advantage of a vector graphic is that they often require less memory than bit-maps do.
In an image, the bit depth is the number of bits used to represent the color of a single pixel in a bitmapped image or video frame buffer. If the bit depth is high (for example 246-bit), then the quality of the image is going to be considerably better compared to an image that only had an 8-bit display. This concept is also known as bits per pixel (bpp), as certain amounts (bits) of memory are assigned to each pixel, this decides how much detail the pixel can allocate. "True-color" or "24-bit" color displays can show millions of unique colors simultaneously on the computer screen. True-color images are composed by dedicating 24 bits of memory to each pixel; 8 each for the red, green, and blue components (8 + 8 + 8 = 24).
The image to the left is an example of an 8-bit image and as you can see the quality is very poor as you can almost see the individual pixels that make up the image. However, the image to the right, is an example of a 246-bit image and as you can see, the image is considerably better quality and sharper that the 8-bit image.
Colour space
Greyscale- A greyscale image refers to an image, or photograph, that only contains shades of gray within it. Less information is needed in each pixel for a greyscale image; therefore, it is differentiated from a RGB image or CMYK image. The end product therefore, is a black and white image.
RGB- The RGB colour model is an additive colour model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors. The main purpose of the RGB color model is for the sensing, representation, and display of images in electronic systems, such as televisions and computers, though it has also been used in conventional photography. Before the electronic age, the RGB color model already had a solid theory behind it, based in human perception of colors.
YUV Colourspace- The Y in YUV stands for "luma," which is brightness, or lightness, and black and white TVs decode only the Y part of the signal. U and V provide color information and are "color difference" signals of blue minus luma (B-Y) and red minus luma (R-Y). Through a process called "color space conversion," the video camera converts the RGB data captured by its sensors into either composite analog signals (YUV) or component versions (analog YPbPr or digital YCbCr). For rendering on screen, all these color spaces must be converted back again to RGB by the TV or display system.
Image Capture
Scanner- A scanners job is to convert an image that a human can understand, into a digital image that can be processed and stored by a computer, coded in the form of millions of numbers (zeros and ones) called binary code.be captured through different equipment for example scanners, digital cameras etc. The scanner does this by moving the scanner head along the picture to copy the image, one line at a time, onto the computer, this process is called scanning, hence why the machine is called a scanner.
Digital Camera- Just like a conventional camera, it has a series of lenses that focus light to create an image of a scene. But instead of focusing this light onto a piece of film, it focuses it onto a semiconductor device that records light electronically. A computer then breaks this electronic information down into digital data, producing a digital image that you then see on the screen of the camera. All the fun and interesting features of digital cameras come as a direct result of this process.
Memory- In a digital camera, the images that are captured, is written onto a memory card. The size of the image depends on the number of megapixels that the image is captured at and also the file format that the camera us using.
Applications of Digital Graphics
Digital graphics is used in many different products in the interactive media sector. Some of the main uses of digital graphics such as; web banners, rollover buttons and menus.
Rollover Buttons
Rollover buttons are created by web designers and they are used to provide the user with some interactivity with the web page. The name 'Rollover' was given to the buttons to correspond with the process of moving the mouse over the button and the button the reacting, usually visually by changing shape or even changing the webpage itself. Basically the look of the button changes when the cursor moves over it. Although you may not notice them, rollover buttons are used a lot across the interactive media sector.
Web Banners
A web banner is a form of advertisement on the internet. This form of advertising consists of embedding the advertisement into a web page. They will normally be placed on a popular website that has a lot of users, such as Facebook or myspace, the advertisement will then have a link to their own website. These banners will often be made up of an image (GIF, Flash, often employing animation, sound, or video to maximize presence)
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