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Working with Image Files

This workshop covers various topics related to image files, including compression, resolution, formats, and applications. It also explores batch processing, working with image sets or sequences, movies, and publications.

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Working with Image Files

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  1. Working with Image Files Aaron Fuegi aarondf@bu.edu SCV Visualization Workshop – Fall 2008

  2. Working with Image Files - Topics SCV Visualization Workshop – Fall 2008 • Image Files • Compression, Resolution, Formats, etc... • Applications • Batch processing • Working with image sets or sequences • Movies • MPEG, DVD • Publications • Resolution • Color space

  3. Image Files • PPM Image File – 24 bit color, 3 pixels by 3 pixels SCV Visualization Workshop – Fall 2008 P3 3 3 255 0 0 0 128 0 0 255 0 0 128 128 128 0 128 0 0 255 0 255 255 255 0 0 128 0 0 255

  4. Image Files - Issues SCV Visualization Workshop – Fall 2008 • Compression • None, Lossless, or Lossy • Huge difference – 100 to 1 file size • Image Size/Resolution • Pixels vs. DPI (Dots per inch) • Web or Printing • Web support – JPEG, PNG, GIF • Color Depth • 24bit vs. 8bit – much less of an issue than it used to be

  5. Image Files - Formats SCV Visualization Workshop – Fall 2008 • JPEG – Web, 24bit, Lossy, Small file size • PNG – Web, 24bit • GIF – Web, 8bit, Color lookup table • TIFF, RGB, PPM – 24bit, Large file size, High quality • PSD – Photoshop’s format • Editable text, Layers, etc… • RAW – Digital camera formats, multiple • MANY others

  6. Image Files - Applications SCV Visualization Workshop – Fall 2008 • Viewing, Resizing, Manipulating Images • Adobe Photoshop • Windows/Macintosh • GUI, Very powerful, Expensive • Most popular general image editing package • XV • Mostly an image viewer but some editing capability • GUI, Linux, Free, Easy to use, No longer being updated • ImageMagick • Command-line tools • Linux, Free

  7. Adobe Photoshop SCV Visualization Workshop – Fall 2008

  8. XV SCV Visualization Workshop – Fall 2008

  9. ImageMagick SCV Visualization Workshop – Fall 2008 • Add a blue border around image (expand?, replace?, shrink?) • convert -border 10x10 -bordercolor "#6699ff" fan.png fan2.png • Add a caption/attribution • convert -font helvetica -fill red -pointsize 14 -draw 'text 446,404 "sondak@bu.edu"' fan2.png fan3.png

  10. ImageMagick - Tools SCV Visualization Workshop – Fall 2008 • Convert • Convert image formats. • Many image transformations available – scale, rotate, text, artistic filters • Display • Import • Screen capture under Linux • Identify • Find out characteristics of image • Composite • Composite multiple images together

  11. Batch Processing SCV Visualization Workshop – Fall 2008 • Working with a set or sequence of images • All images generally must be the same size • Adobe Photoshop • Recording and applying actions • Perl (or another computer language) • Extremely flexible but requires programming background or help • Augments command-line tools such as ImageMagick

  12. Movies SCV Visualization Workshop – Fall 2008 • ImageMagick (Animated GIFs only) • convert -delay 20 –loop 0 file*.gif anim.gif • animate anim.gif • Adobe Premiere • Movies • Displaying on computer or DVD? • Formats – QuickTime or AVI • Adobe Encore • DVDs • Menus, Controls, Chapters, etc…

  13. Images in Publications SCV Visualization Workshop – Fall 2008 • Resolution • Web – generally around 100 DPI • Print – generally 600 DPI – match journal specifications • Re-render image at very large scale. Do not just scale up. • File Format • Use a lossless 24-bit color format such as TIFF or PNG • Color Space • Web – RGB (standard) • Print – CMYK • Printing • Color gamut – Additive vs. subtractive color

  14. Working with Image Files - Questions? Aaron Fuegi aarondf@bu.edu SCV Visualization Workshop – Fall 2008

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