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Introduction to Computer Graphics
Film-based photography was the
foundation for graphic reproduction
starting in early 1900s
Raster/paint software developed to work
with scanned images
Adobe Photoshop: Dominant image-
editing program and electronic painting
software program in world
Raster/Paint Software
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Introduction to Computer Graphics
Bitmap-based application
– Every image made up of a series of dots
called pixels
Wide range of tools to adjust and correct
color, contrast and dynamic range
Powerful type handling tools
Capable of handling web-based graphics
Photoshop: An Overview
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Introduction to Computer Graphics
Film-based images
Scanners
Digital Image Capture
How Are Photographic
Images Created?
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Introduction to Computer Graphics
Film-based Images
Emulsions
Prints
Transparency film
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Introduction to Computer Graphics
Raster art or Bitmapped art
– Series of dots arranged in a grid
– Dots vary in value and color
Resolution
Color Models
File formats
Resolution and Color
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Introduction to Computer Graphics
Resolution
Number of dots that make up an image
Raster images are resolution dependent
Four ways to measure resolution
– LPI: Lines per inch
– SPI: Spots per inch
– DPI: Dots per inch
– PPI: Pixels per inch
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Introduction to Computer Graphics
Color Models
Three important color models
RGB as a design tool
– Red, green, blue
– Additive primary colors
CMYK for color correction
– Cyan, Magenta, Yellow, Black
– Subtractive color
Grayscale
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Introduction to Computer Graphics
Open and Save Files
Working with Documents
File>New
– Size
– Orientation: Portrait or Landscape
– Color Mode: Another name for color model
– Background contents
File>Open
File>Save
File>Save As
File>Save for web
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Introduction to Computer Graphics
File Formats
.PSD: Photoshop Document
– Native Photoshop format,
– Preserves layers
– Access to all tools
and commands
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Introduction to Computer Graphics
File Formats
.TIF: Tagged Image File Format
– Any resolution, grayscale or color
– Generally used for graphics files to be printed
.EPS: Encapsulated Postscript
– Specialized format for bitmap or vector graphics
.JPG: Joint Photographic Experts Group
– Compressed image format
– Often used for complex photographic images
.GIF: Graphics Interchange Format
– Used specifically for the Web
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Introduction to Computer Graphics
Everyday Tools
and Commands
Photoshop interface similar to Illustrator
Rulers and Guides used to position
elements on the page
Toolbox basics
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Introduction to Computer Graphics
Toolbox
Divided into 4 main areas
– Selection tools
– Cropping tools
– Modification tools; clone stamp, history brush,
eraser, gradient, blur/sharpen tools
– Vector/type tools
– Miscellaneous tools; eyedropper, zoom tools
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Introduction to Computer Graphics
Selection Tools
Main selection tools: Marquee selection
tools, Move tool, Lasso tools, Magic
Wand tool, and Slice tool
Crop tool is part of main selection tools,
to reduce
file size as
well as a
design
decision
tool
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Introduction to Computer Graphics
Modification Tools
Manipulate images in various ways
Fix damaged photographs
Paint or draw on images
Copy parts of images
Restore pixels deleted or erased
Color gradients
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Introduction to Computer Graphics
Vector/Type Tools
Although primarily used to work with
bitmapped images, Photoshop contains a
comprehensive array of type and vector-
based tools
Vector/type tools similar to Illustrator
Eventually the vector shapes are
converted to dots when file is saved to a
format other than native .psd
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Introduction to Computer Graphics
Miscellaneous Tools
Perform a variety of tasks such as
magnification, color identification in a
specific area of an image, and electronic
sticky-type notes
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Introduction to Computer Graphics
Modify only a portion of an image
Create photomontage that use only pieces
of images
Selection tools include
– Marquee selection tools
– Lasso tools
– Magic wand tool
The Power of Selection!
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Introduction to Computer Graphics
Rectangles or squares
Ovals or circles
Single row pixels horizontally and vertically
Marquee Selection Tool
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Introduction to Computer Graphics
Surround portion of image with a line
Accuracy of selection depends on accuracy
of mouse movements or pen and tablet
Three variations
– Lasso
– Magnetic Lasso
– Polygonal Lasso
Lasso Tools
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Introduction to Computer Graphics
Attempts to select a range of values,
based on 256 color values
Tolerance lets you set the range of values
– Smaller tolerance number; the narrower the
value range (color and shades) of the selection
– Higher tolerance numbers; the wider the value
range of a selection
Tool works best is image has well defined
areas of value
Magic Wand Tool
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Introduction to Computer Graphics
It All Works with Layers
Using layers, Photoshop separates
multiple images onto transparent layers
Can manipulate each layer without
affecting other images in project
Layer Effects can add excitement and
dynamics to design
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Introduction to Computer Graphics
Working with Layers
Layers palette is control center for
layers in a file
Background layer has special properties
Can add, delete, duplicate layers
Change layering order
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Introduction to Computer Graphics
Layers Effects
Special effects to add visual impact, such
as blending, drop shadows, color
overlays, bevel and emboss
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Introduction to Computer Graphics
Transformation tools give power and
control over images
Healing Brush and Patch tools
Clone Stamp tool
Eraser tool
Blur, Sharpen, and Smudge tools
Dodge, Burn, and Sponge tools
Transforming Images
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Introduction to Computer Graphics
Use brush size to regulate selected and
modified area
Valuable for fixing old
and/or damaged photos
Areas repaired blend
in with adjoining areas
Healing Brush and Patch
Tools
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Introduction to Computer Graphics
Samples a particular
section of an image
and recreates it over
and over again
Also used to cover
up areas of a photo
with different imagery
Clone Stamp Tool
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Introduction to Computer Graphics
Alters specific parts of
an image
Works by clicking and
dragging mouse
Options allow
fine-tuning of tool
effect
Blur, Sharpen, and Smudge
Tools
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Introduction to Computer Graphics
Related to
traditional film-
based photography
Burn tool
darkens an
image; Dodge tool
lightens it
Sponge heightens
or mutes color
Dodge, Burn, and Sponge
Tools
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Introduction to Computer Graphics
Photoshop Has
Too Much Fun with Type
Dedicated Type Layer
Similar to vector-draw programs
Character palette lets you change
– Type size
– Leading
– Alignment
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Introduction to Computer Graphics
Photoshop Has
Too Much Fun with Type
Transformation tools work on type too!
Layer effects applied to type
Warp type: still remains editable after warp
effect is applied
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Introduction to Computer Graphics
Designers don’t normally output
Photoshop directly from application
More often imported into another
application, then output from there
Print preview dialog box allows for
selection of printer, number of copies,
scaled outputs and output modes
How Photoshop Files Are
Output
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Introduction to Computer Graphics
Photoshop lets you color-manage the
output to create more consistent color
output between different devices
Printing Tools in Photoshop
