Computer Graphics and Imaging Concepts Quiz

Essential Concepts in Computer Graphics

• A pixel (or pel) is the smallest unit of a digital image or graphic that can be displayed on a digital display device.

• Resolution is the number of distinct pixels in each dimension that can be displayed on a monitor or display device. A common resolution is 1024 x 768.

• Aspect ratio describes the correlation between width and height of an image or screen. Common aspect ratios include 4:3, 16:9, and 21:9.

• DPI (dots per inch) and PPI (pixels per inch) both measure the resolution of an image or digital screen. They represent the number of dots or pixels within a one-inch line.

• A frame is a rigid structure surrounding something, like a picture, door, or windowpane or, in video and animation, an individual picture in a sequence. Frames are rectangular areas used to insert graphics and text.

• Saturation is the depth or intensity of color in an image. Higher saturation means more vibrant color, while lower saturation makes colors appear subdued or muted.

• Contrast describes the relationship between the darkest and brightest parts of an image. High contrast means a large difference between light and dark areas, while low contrast means a smaller difference.

• Rasterization is the technique of converting vector graphics to pixels for output on a screen.

• Aliasing occurs when the resolution of the graphics device or file is not high enough to represent a smooth curve, resulting in jagged lines or curves.

• Foreshortening is a technique that creates an illusion of projection or extension in space when representing an object or human body in a picture.

• Flickering is the appearance of flashing or unsteadiness in an image on a display screen, often caused by a low video refresh rate.

• Halftone is a reprographic technique for simulating continuous-tone imagery through the use of dots, with varying sizes or spacing to create the illusion of continuous tone.

• Dithering is a technique to fool the eye into seeing more colors on a screen by mixing different colored pixels.

Display Technologies

• A display device is a device used to view video, images, or text. Examples include TV monitors, mobile screens, and desktop monitors.

Video Display Devices

• Different types of video display devices include Cathode-ray tube (CRT) monitors, Liquid crystal displays (LCDs), Light Emitting Diode (LED) displays, Direct View Storage Tubes (DVSTs), Plasma displays, and 3D displays.

Cathode-ray tube (CRT) Monitors

• CRT monitors are a primary video output device, using a cathode ray tube to display images.

Refresh CRT

• The refresh rate is the frequency at which an image is redrawn on a CRT screen. A higher refresh rate reduces flickering.

• Resolution refers to the maximum number of points that can be displayed on a CRT display device.

CRT Display Principles

• Raster-scan displays work by using an electron beam that sweeps across the screen, creating images row by row.

• Interlaced scanning method reduces flickering by displaying even numbered lines of the picture on one scan pass and the odd-numbered lines on a separate pass.

• The frame buffer is memory where picture data is stored for display on the screen. This data includes the pixel depth, which determine the color resolution of the display.

Frame Buffer

• A frame buffer is memory that stores the image information for the screen display. Variables that describe the buffer's characteristics include size, X and Y coordinates, and pixel depth. It affects the resolution; for instance, 1024 x 1024.

• Bit planes or bit depth determine the number of bits per pixel. For example, a 24-bit frame buffer stores full color (millions of colors).

Specifying Color

• Direct color refers to assigning a specific color value to each pixel. Example: 24 bits where R,G,B are used.
• Palette-based color (CLUT) uses a palette to map pixel color values to a limited set of colors. For example: 8-bit palette represents 256 different colors.

Interlaced Scanning

• To reduce flickering, a frame is divided into fields, odd and even scan lines are displayed alternately. This produces an interlaced image

Flat-Panel Displays

• Flat-panel displays are an alternative to CRTs, characterized by reduced volume, weight, and power consumption.

• Two main categories are emissive displays (e.g., plasma) and non-emissive displays (e.g., LCDs).

Plasma Panel Display

• Plasma panels are emissive displays that use a gas mixture in between two glass plates.

Liquid Crystal Displays (LCDs)

• LCDs use liquid crystals and passive or active matrix technologies to control light transmission.

3D Display

• 3D displays provide depth perception to the viewer, and examples include fog display, holographic display, and retina display. Advantages include impressive picture quality, but disadvantages include high cost.

Video Output Devices

• Various video output devices including desktop, vector displays, CRT, LCD flat-panel, plasma, workstation displays, PC/Mac laptops, tablet computers, Wacom’s display tablets, digital projectors, Field Emission Devices, and OLED displays, as well as various input devices.

Traditional Input Device

• Traditional input devices encompass mouse-like devices (mouse, wheel mouse, trackball), keyboards, pen-based devices (pressure-sensitive tablets, IPAQ, Microsoft tablets, palm-top devices), joysticks, game pads, flight sticks, touchscreens, microphones (wired/wireless headsets).

3D Input Devices

• 3D input devices include electromagnetic trackers (such as Polhemus FASTRAK), gloves that track hand movements, and others.

Display Processor

• The display processor digitizes picture definitions, converting them into pixel intensity values for storage in the frame buffer.

Graphics Software

• Graphics software consists of programs used to create and manipulate images and models.

• Types include special purpose packages (user-friendly menu-driven), and general purpose packages (programming languages).

Graphic Standards

• Graphic standards are agreed specifications that dictate how various computer subsystems communicate and interface.

Important Note:

• There was a quiz announcement for next week, online between 6 PM and 6:15 PM.