1. C
om
Computer Graphics:
pu
A Brief Introduction
te
rG
ra
ph
ic
1 s

2. Overview
• Purpose
• Terminology & concept
C
om
• Formats
pu
• Use of computer graphics
te
– Electronic Publications
rG
– Print Publications
ra
ph
– Presentations and Websites
ic
• Softwares
2 s

3. Purpose
• The right format for the right application
• Incorrect format/resolution may lead to:
C
– Bloated PPT presentations (if it’s >30 MB with no video,
om
you’re doing it wrong)
– Bloated documents (particularly dissertations)
pu
• Microsoft Word hates big documents
te
– Blurry images (particularly in print)
rG
– Irate editors
ra
ph
This 23-slide image-only presentation
can definitely be optimized…
ic
3 s

4. Terminology
• Raster vs. vector
– Raster (bitmap)
C
• Defines color of each
om
pixel in a bitmap
pu
• Good for photographs
te
• Limited scalability
rG
• Most common format
– Vector
ra
ph
• Defines starting points
and paths
ic
s
• Good for simple shapes
(logos)
• Scalable, suitable for use
4 in banners

5. Terminology
• Resolution (for raster images)
– Typically expressed in dpi (dots per inch) or similar
– Defines how many pixels (bit) per inch – higher resolution allows
C
more detail per inch
om
• 900 x 600 pixel image at 300 dpi has print size of 3” x 2”
pu
– 72 dpi for screen display (presentations, websites)
– >200 dpi for print publications (journals, brochures, books)
te
– Most journal wants at least 300 dpi
rG
• Compression
ra
– None: largest file size, most compatible
ph
– Lossless: can be converted to original reversibly
– Lossy: loss of original information during compression, typically
ic
smaller file size
s
– Usually relevant only when image is saved as stand-alone instead of
being embedded – word processors or presentation software will
attempt to compress regardless
5

6. Optimizing Files with Embedded Images
• A bloated .ppt or .doc file typically has embedded
images with large pixel count
• Resizing images in MS Powerpoint or Word does
C
om
NOT modify pixel count
• Modern digital photographs typically have little
pu
compression and large pixel count (justified by its
te
potential use in print)
rG
– Using images directly from a 8 MP (megapixel) camera
to .ppt or .doc = guaranteed bloat
ra
• Optimized image should have the correct
ph
dimensions with minimally acceptable resolution
ic
without further resizing
s
• Image manipulation software is essential in
adjusting actual pixel count!
6

7. Raster File Formats
• For more information:
http://en.wikipedia.org/wiki/Comparison_of_graphics_file_formats
• BMP
C
– Raster, no compression
om
– Large file size in disk (direct relation to pixel count)
pu
– Default output of MS Paint
te
– Generally word processing/presentation software will compress
rG
internally
• JPEG (Joint Photographic Experts Group)
ra
– Both a file format and method of compression
ph
– Raster, lossy compression (the “MP3 of digital photos”)
ic
– File size depends on both pixel count and compression quality
s
– Generally preferred for photographs & paintings with smooth
variations of tone and color
7

8. Raster File Formats
• GIF (Graphic Interchange Format)
– Raster, lossless (LZW) compression
– Limited color depth (256 color)
C
om
– Small file size
– Supports transparency and animation
pu
– Still primarily used for animated pictures on websites
te
• PNG (Portable Network Graphics)
rG
– Developed to improve upon GIF
– Raster, lossless compression
ra
– Greater color depth (24-bit RGB), allowing more subtle tone and color
ph
than GIF
– Supports transparency
ic
s
– Small file size (comparable to GIF)
– Preferred for text and line arts with sharp transitions (e.g., logos)
8

9. Vector File Formats
• EPS (Encapsulated PostScript)
– Subset of PDF
C
– Widely supported in publishing programs
om
– Preferred format for logos – allows unlimited
pu
scaling with small file size
te
– No browser support
rG
• SVG (Scalable Vector Graphics)
ra
– Allows static and animated images
ph
– Less widely supported
ic
– Limited browser support (Safari, Opera)
9 s

10. The Power of Vector Graphic Format
C
om
pu
te
rG
ra
ph
ic
10 s

11. Raster File Format
• TIFF (Tagged Image File Format)
– Raster graphics, may contain some vector
C
information
om
– Any compression: none, lossless, lossy (JPG)
pu
– May contain additional information (e.g., camera
te
rG
model) stored in ‘tags’
ra
– Due to flexibility, not suitable for use in web
ph
browsers
ic
– The preferred standard for printing and scanning
11 s

12. Electronic Publications
• Includes papers, reports, and dissertation
• May be read in either print or electronic format
C
om
• Resolution 200-300 dpi without resizing unless
pu
specified otherwise
te
– Enough to be printed well on standard paper
rG
– Not too large in size (must optimize)
ra
• Usual formats: JPG, PNG, TIFF, EPS (less
ph
ic
common)
12 s

13. Print Publications
• Includes brochures, books, portraits, pocket
guides
C
om
• Must have high resolution, >300 dpi (based on
final print size) recommended
pu
te
• Usual formats: TIFF, PNG, JPG, EPS
rG
• Use vector graphics whenever possible to reduce
ra
file size (e.g., ICOM’08 banner is saved in vector
ph
form)
ic
s
• In general, size is of secondary importance
13

14. Presentations and Websites
• Viewed either in browsers or projected on
screen
C
om
• Resolution of 72-144 dpi, without resizing
pu
• Smaller size means more responsive
te
presentation or webpage
rG
• Usual formats: JPG, PNG, GIF
ra
ph
• Use animations sparingly!
ic
14 s

15. Image Manipulation Software
• Raster
– Adobe Photoshop (Windows/Mac)
C
– Microsoft Paint (Windows, very limited features)
om
– Microsoft Office Picture Manager / Photo Editor (MS Office
suite, limited features)
pu
– GIMP (GNU Image Manipulation Program):
te
http://www.gimp.org (Windows/Mac/Linux)
rG
• Vector
ra
– Adobe Illustrator (Windows/Mac)
ph
– Adobe Flash (Windows/Mac, geared toward animation)
ic
– Inkscape: http://www.inkscape.org (Windows/Mac/Linux)
s
– OpenOffice.org Draw (Windows/Mac/Linux)
16

16. Manipulating Image Size
• Work with image with highest detail (highest
pixel count) as possible
C
– You cannot turn low res image into higher res
om
without reducing size proportionally
pu
– Example: 12” x 8” image at 72 dpi can be turned
te
into 3” x 2” image at 288 dpi (pixel count remains
rG
the same: 864 x 576 px.)
ra
• Image manipulation program will attempt to
ph
interpolate when pixel count changes
ic
– Quality tends to be better preserved when px. count
s
decreases rather than increases
17

17. Conclusion
• Bloated file? Try resizing some images using
image manipulation software
C
om
• General rule for resolution:
pu
– 72 dpi for electronic
te
– 300 dpi for print (when in doubt, print out!)
rG
ra
ph
ic
18 s