S6/CA/Graphic/P.1
CUHK FAA Thomas Cheung Secondary School
S6 Computer Applications
Graphics
Name :
Class:
Class No.:
1. Concepts and Terminology
1.1 Pixel
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short for Picture element
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a single point (i.e., smallest element) in a graphic image, such as a letter, a number or a graphics
picture
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graphics monitors display pictures by dividing the display screen into thousands (or millions) of
pixels, arranged in rows and columns.
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pixels are so close together that they appear connected
each pixel is assigned a binary codes specifying location and colour value
the number of bits used to represent each pixel determines how many colors or shades of gray can
be displayed.
VGA (short for Video Graphics Array, which is a graphics display system for PCs developed by
IBM in 1987) systems display 640 by 480, or about 300,000 pixels
SVGA (Super VGA) systems display 800 by 600, or 480,000 pixels
True Colour systems use 24 bits per pixel, allowing them to display more than 16 million different
colors
1.2 Resolution, colours, grayscale, clipart
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B.
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C.
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D.
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Resolution
the quality of a display system largely depends on its resolution, how many pixels it can
display, and how many bits are used to represent each pixel
the fineness of details attained by a printer, or a monitor in producing an image
measured in dots per inch, or dpi
Colours
more number of bits, the higher representation of colours
1 bit, 2 colours; black and white
4 bits, 16 colours
8 bits, 256 colours
16 bits, 65536 colours; high colour
24 bits, 224 colours.
VGA system has a resolution of either 640 by 480 (with 16 colors) or 320 by 200 (with 256
colors)
True Colours
Refers to any graphics device or software that uses at least 24 bits to represent each dot or
pixel
Using 24 bits means that more than 16 million unique colours can be represented. Since
humans can only distinguish a few million colours, this is more than enough to accurately
represent any colour image
Grayscale
a colour mode that is made up of 256 shades of gray
S6/CA/Graphic/P.2
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the 256 colours include absolute black, absolute white, and 254 shades of gray in-between
black and white
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images in grayscale mode are represented in 8 bits
e.g., black and white photographic images are the most common examples of the grayscale
color mode
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E.
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Clipart
ready-to-use graphic images provided by software companies
usually bundled with application software, also available in stand-alone package
e.g. Taskforce, MS Clipart gallery
1.3 Bitmap Graphics
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also called raster images
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use a grid of small squares known as pixels to represent images
resolution-dependent; that is, it contains a fixed number of pixels to represent its image data. As a
result, a bitmap image can lose detail and appear jagged if viewed at a high magnification
on-screen or printed at too low a resolution
suitable for representing subtle gradations of shades and colour; e.g., in photographs or painted
images
software: PaintBrush, Photoshop, PaintShop Pro, Photo Impact
popular formats: bmp, pcx, gif, jpg, png, rle, dib
1.4 Vector or Object-Oriented Graphics
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made of lines and curves defined by mathematical objects called vectors
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describe graphics according to their geometric characteristics – position, length and direction
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e.g., a bicycle tire in a vector graphic is made up of a mathematical definition of a circle drawn
with a certain radius, set at a specific location, and filled with a specific colour
can move, resize, group, ungroup or change the colours of the objects without losing the quality of
the graphic
resolution-independent; that is, it can be scaled to any size and printed on any output device at any
resolution without losing its detail or clarity
suitable for type and bold graphics that must retain sharp lines when scaled to various sizes; e.g.,
logos
software: CorelDraw, AutoCAD
file formats: wmf, eps, emf, cdr
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2. Creating and Editing a Graphic Image
2.1 Drawing shapes
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Line object
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AutoShape objects
2.2 Editing graphic images
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Change line style and colour
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Filling drawing objects with solid colour, pattern and textures
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Adding shadows
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3-D extruding
S6/CA/Graphic/P.3
2.3 Transformation of graphic images
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Moving drawing objects
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Resizing drawing objects
Changing shapes
Adjusting objects
Rotating and flipping drawing objects
Duplicating drawing objects
2.4 Transformation of graphic images
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Moving drawing objects
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Resizing drawing objects
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Changing shapes
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Adjusting objects
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Rotating and flipping drawing objects
Duplicating drawing objects
2.5 Grouping, ungrouping and layering
2.6 Loading, saving and printing graphical files
3. Importing and Exporting of Graphics
3.1 Capturing and Importing of Graphic Images
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From clipart library
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From image scanner
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From digital camera
3.2 Exporting of Graphic Images
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To printer or plotter (as hard copy)
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To web page (as soft copy)
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To different file formats