Computer Graphics Brief Tutorial

Computer Graphics Brief Tutorial

• 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
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  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
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  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
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  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
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  Optimizing Files withEmbedded 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
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  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
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  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
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  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
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  The Power ofVector Graphic Format C om pu te rG ra ph ic 10 s
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  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
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  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
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  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
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  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
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  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
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  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
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  Conclusion • Bloatedfile? 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