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image editing package • XV • Mostly an image viewer but some editing capability • GUI, Linux, Free, Easy to use, No longer being updated • ImageMagick • Command-line tools • Linux, Free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