Computer Science 1033A/B Study Guide - Final Guide: Desktop Publishing, Word Processor, Coreldraw
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15 Apr 2012
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GRAPHICS
We rely on images for – Information, explanations, entertainment
Graphics originate from: non-digital medium (paper copy of a photo), outside world, create image
DIGITIZATION: the process of translating a piece of information (text, images, sound recording,
video) into BINARY BITS
BIT: short for Binary Digit, value of “1” or “0” – fundamental units of information in a
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When press a key, binary code sent to RAM (memory) CPU Video card On
screen
Measurement system – binary system (base of 2, exponent = number of bits)
BYTE: collection of 8 bits (28) = 256 possible combinations of 1s and 0s
Ex: 21 = 2 values (0, 1), 22 = 4 values (00, 01, 10, 11)...
IMAGE: represented by a grid (array, matrix) of squared picture elements called PIXELS (the
smallest image component and thus shows the smallest detail)
Pixel – numerical value corresponding to a COLOR INDICATOR (bw or colour)
RGB Code
Hexadecimal Code
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een – 640 dots on each of 480 rows 300,000 pixels
Coding colors
Black/white = 1 bit ONLY (0 = black, 1 = white)
2 bits – combination of black and white (01/10) grey
More bits, more shades... 4 bits 24 = 16 grey shades
Used for web
Used for printing
Additive Model (RGB)
Subtractive Model (CMYK) (k=black)
Primary colours: Red, Green, Blue
Primary colours: Cyan, Magenta, yellow
“added” to a black background in order to obtain
color shades
“subtracted” from a white background
In “TRUE COLOR” each pixel represents some color shade – Uses 24 bit representation = 16
million colors
Color can be expressed in:
RGB does not = Hexadecimal, need converter
Cathode ray tube devices (such as computer monitors) can only display colour with red,
green and blue light – this is the color system of the web
Each pixel is represented by 3 values
-ie: light yellow = <255,255,127> <R,G,B>
Syntax:
Each value ranges from 0-255
256 color shades = 28 bits
-16 million colors in the spectrum (2563)
-consists of 16 unique symbols:
0,1,2,3,4,5,6,7,8,9,E, and F
-color represented by 6 digits: ie, #FFCC66
Red: <255,0,0>
Green: <0,255,0>
Blue: <0,0, 255>
Red: #FF0000
Green: #00FF00
Blue: #0000FF
-Web-safe colors: only 1,3,6,9,C,F
Types of Graphics – Bitmap or vector – effects how graphics are displayed on a computer screen:
Quality, file size, time to display graphics
BITMAP (zoom in to pixels)
VECTOR (zoom in, no pixels)
-images made up of small squares called Pixels
-Editing pixels: changing color, shade, brightness
Advantages of using a small image rather than larger:
-shorter time needed to display on screen
-smaller file size
Disadvantages:
-distortion occurs when image is enlarged
-image is represented with lines and arcs that have a
mathematical relationship
-describes the drawing of the shape
- Line: starting point, direction length
- Rectangle: start point, width height
- Circle: center and radius
*SMALLER FILE: records mathematical relationship
-as image is enlarged (resized):
- Dots become larger, edges more jagged
- Quality decreases
- File size increases
-as image enlarged (resized):
- Dots become larger, edges still clean, crisp
- Quality is maintained – no distortion
- File size increase
**Vector CANNOT be converted to Bitmap, but Bitmap CAN be converted to vector
BITMAP-BASED programs “PAINT”
VECTOR Graphics programs – “DRAW”
-ability to edit an image’s pixels
-images from scanners, cameras
-need a “PAINT” program
-greater control and precision with free-hand tool
-display more accurately on screen
-download faster because support of Flash and Scalable
Vector Graphics (SVG formats)
-produce smaller files that download faster
-more details in vector-based illustrations
-must use a “DRAW” program – draw and edit paths
Photoshop, paintshop pro, photoplus
(but photoshop v6.0 has vector features)
Adobe illustrator or Macromedia FreeHand, Corel Draw
Graphic Attributes IMAGE QUALITY: Image resolution, image bit depth
IMAGE RESOLUTION (ppi/dpi): the number and spacing of pixels in an image
The number of pixels per square inch on a computer-generated display
Ex: if resolution 100 ppi, each pixel 1/100th inch
When you increase the number of pixels, increase quality of detail in the
resolution
For different output delivery:
Web – set to 72 dpi (smaller graphics, don’t see detail)