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

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

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

4. Image Files - Issues 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 SCV Visualization Workshop – Fall 2008

5. Image Files - Formats 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 SCV Visualization Workshop – Fall 2008

6. Image Files - Applications 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general image editing package XV –Mostly an image viewer but some editing capability –GUI, Linux, Free, Easy to use, No longer being updated ImageMagick –Command-line tools –Linux, Free SCV Visualization Workshop – Fall 2008

7. Adobe Photoshop SCV Visualization Workshop – Fall 2008

8. XV

9. ImageMagick 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 SCV Visualization Workshop – Fall 2008

10. ImageMagick - Tools 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 SCV Visualization Workshop – Fall 2008

11. Batch Processing 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 SCV Visualization Workshop – Fall 2008

12. Movies 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… SCV Visualization Workshop – Fall 2008

13. Images in Publications 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 SCV Visualization Workshop – Fall 2008

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