Bit-Mapped vs Vector

There are two categories of graphic files, each containing several popular types of files.  The type of the image file is denoted by the 3-letter extension of the file name.  The most common are bmp, gif, and jpg files.  The various formats are used for presentations, diagrams, websites, and instructional documentation.  All images fall into one of two categories :

Bit-Mapped - these files are simply a grid of dots - the "bits" are the dots, and they are "mapped" into a 2-dimensional rectangle.  Since each dot requires info to be saved in the file - they are also the largest files, and rather wasteful.  BMP, GIF, and JPEG files are the most famous bit-mapped files.  They all use compression to reduce the file size, but JPEG and GIF do a much better job of it than BMP.  The file extensions are  .bmp, .gif, or .jpg.  Bit-mapped files become blurry when the size is increased, since the dots must be replicated, and the details lose their crispness.  

Vector  - vector graphics uses a mathematical formula to describe the image, and this results in small file sizes, as well as clarity when increasing the size.  Unfortunately, since a formula is used - the amount of detail is limited.  The most popular Vector graphcs files have the extensions .ai (Adobe Illustrator), .wmf (Windows Metafile Format) and .emf (Enhanced Metafile Format) - both by Microsoft.  Netviz uses it's own proprietary vector graphics files .nvm (NetViz Metafile).  Unfortunately, these file types cannot be created by any software that Sprint users have available - so all you can do is insert the files if available, into a Word document.  Clip-art that is included with Word is also vector-format files, and can be stretched or shrunk and still retain clarity.  Surprisingly, the clip-art included with Microsoft Office is largely composed of rudimentary, and frankly unattractive images.

The Scaling Problem

Vector is scalable with no loss of image clarity but it only allows simplistic images.  Images such as a person or an object must be simplified down into basic lines, rectangles, and circles.  Also there are few applications that can create and edit vector based images (Adobe Illustrator is the most common vector graphics package).  Many applications allows vector graphics to be inserted (Word, Powerpoint, etc.), but they cannot edit the images.  Bit-mapped images are extremely common, they can be complex, and are supported by numerous applications such as adobe Photoshop.  The main drawback to bit-mapped images, is that they do not scale well, and suffer quality degradation upon resizing.

Bit-Mapped Scaling Problem - while most files are bit-mapped, they do not scale well.  If you must resize a bit-mapped image, hopefully it will be to shrink it.  Enlarging files will always result in significant blurring.  The following file has been resized, to show the difference between Bit-Mapped and Vector graphics.   As noted, the vector image (used Netviz to resize) is crisp and clear in all cases.  The bit-mapped image (used Adobe Photoshop to resize) suffers from the resize procedure  The default original, sharp image is shown in the middle, with the ends files being resized.:


Vector Images - effects of resizing



Bit-Mapped Images - effects of resizing

Resizing Bit-Mapped Images - The Golden Rule

Obtain a large initial Image - OR - resize in half

Large bit-mapped images can be sized down and retain most of their clarity.  The previous example begins with a fairly small image (the center image).  So, if you do not have a large image to begin with, then the only option is to keep it as is.  If you must resize a small image, select the resize dimensions to be exactly half of the original - which will simplify the resize process (it simply averages every two pixels, and does not have to interpolate).  For the example, imagine that you need the image size on the right, and that you do have a large original bit-mapped image.  The following shows the original on the left, and the resized image on the right.


As you can see - the key is to have a large image to begin with.


Obtaining Images

As mentioned, Sprint computer configurations do not include graphics packages to create images.  You can download any of the graphics included on this site.  For hard copies that need to be scanned, drop by the proposal group on the 6th floor for a scan.  For various images and clip-art, here are a few sites that contain a wide variety  :

Icon Bazaar            Companion Software            ClipArt Connection         

How to Resize Images

Most of the Sprint proposal personnel use Adobe Photoshop, which unfortunately, is not included on the default Toshiba configuration.  The only image editor that comes with Windows is called "Paintbrush" (Start/Programs/Accessories/Paint), and it is very limited in function.  To resize an image, open it in PaintBrush, and click "Image/Stretch-Skew . . .", and then enter the new size as a percent of height and width in the "Stretch" settings.   This does not allow exact dimensions to be entered - so if you must have an image resized precisely, email the image to your proposal group, and indicate what size you need.