INST 346
Spring 2018
Homework 2

This assignment is due by ELMS before the start of the class session indicated on the syllabus.

1. Use Google or Bing image search to obtain a photograph of a spacecraft. Do not select a drawing; use an actual photograph. Download that image to your hard drive and then use the file explorer to determine its size (e.g. in kilobytes or megabytes).
2. Use an image processing tool that allows you to select the amount of JPEG compression to create JPEG files with different compression levels. I recommend that you use Adobe Photoshop, which is available free to University of Maryland students at TerpWare in the Creative Cloud Apps (which are in the Design and Production category). To change the compression setting of a JPEG image (i.e., one with a .jpg file type), just save it as JPEG and Photoshop will ask you what image quality you want. Note that you will need to use an image editor to see your saved files after you have compressed them; Photoshop will continue to show you the original even after saving it with a different amount of compression. If you have trouble installing Photoshop, you could instead use an online converter such as JPEG Optimizer (of you use that one, uncheck the box for resizing the photo since you should keep the dimensions of all your pictures the same to facilitate comparisons). Different systems have different ways of expressing how much compression is being applied: some say compress to 30%, some say the same thing as compress by 70%, and Photoshop simply offers values between 0 (most compressed) and 12 (least compressed). Try several values, include at least one very extreme (i.e., highly compressed) compression value. For each compression value you try, report the resulting file size. You can do this using a table or a graph.
3. Now inspect your most highly compressed image using an image viewer, and describe (using words) the kinds of problems that you see from using that level of compression. You may need to zoom in to inspect regions of the photo in detail to see the problems if you are using Photoshop (which limits how much compression you can apply).
4. Now repeat the process for this image of a document from the John F. Kennedy Presidential Library. Again show a table or graph of file sizes and compression levels.
5. Again describe the kinds of problems that you see for the most highly compressed version of this document image.
6. The kinds of problems that you see should be different for your spacecraft image and for the Kennedy Library document. Explain why that is so.