Working with Image Files

Working with Image FilesWorking with Image Files

Aaron [email protected]

IS&T Scientific Visualization Tutorial – Spring 2010

Working with Image Files - TopicsWorking 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


Image FilesImage Files

P33 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


• PPM Image File – 24 bit color, 3 pixels by 3 pixels

Image Files - IssuesImage 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


Image Files - FormatsImage 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


Image Files - ApplicationsImage 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XV– Mostly an image viewer but some editing capability– GUI, Linux, Free, Easy to use, No longer being updated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


Adobe PhotoshopAdobe Photoshop


XVXV


ImageMagickImageMagick 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 "[email protected]"' fan2.png fan3.png


ImageMagick - ToolsImageMagick - 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


Batch ProcessingBatch 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


MoviesMovies 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…


Images in PublicationsImages 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


Working with Image Files - Questions?Working with Image Files - Questions?

Aaron [email protected]

http://scv.bu.edu/documentation/tutorials/ImageFiles/


mailto:[email protected]

Working with Image Files

Documents

image viewer

image sets

image filesaaron

image filesp33

ppm image file

image files formatsjpeg

small file sizepng web

large file size