Encoding Digital Images

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Updated on May 22, 2013

Whether you are taking photos with your iPhone, watching a DVD, reading a pdf, or checking out Google images, digital images are everywhere. This is quite amazing because these images require a lot of memory. The memory required by these complex images makes them hard to store and time-consuming to download.

Almost everyone is familiar with pixels – the rows of tiny dots that make up an image. The resolution of an image depends upon the number of pixels used in a particular image. A raster image is a data structure that stores information about those pixels. The data about these pixels is compressed, using a particular encoding algorithm so that the image takes up less memory. A lossless algorithm permits the image to be reproduced without losing any information. A lossy algorithm is one in which some of the data is lost so that the image can be compressed even more.


Which method of digital image compression results in the best-quality photos?

  • Computer
  • Printer
  • Assistant
  • Internet access or a library of different photo images stored on the computer.


  1. Select at least two images. The first image should be a nature image with expansive blue sky, ocean or other repetitive information. The second image should be a busy urban scene. If you select a third image, it should be black and white.
  2. Determine how to save your images in difference formats.For example, if you are working in MAC OS X, find a image in your document. Open the document in “Preview.”Click on “File” to open the drop-down menu. Click on “Save As.”Select a particular format (TIFF, pdf, JIF, PNG etc.) under “Format” and then click on “Save.”
  3. Save the same image in a variety of formats.
  4. Have your assistant print the image. The assistant should mark the image with a code number that is associated with the format. For example, all jpegs can be marked “#1,” all TIFFs can be marked “2,” and so on. Only the assistant knows what formats are associated with which numbers.
  5. Closely examine the printed images. Pay close attention to the fine details of the image. Are all the images identical? Which are better?
  6. Research which formats involve lossy coding and which involve lossless coding.
Cy Ashley Webb is a science writer. In addition to having worked as a bench scientist and patent agent, she judges science fairs in the San Francisco bay area. She loves working with kids and inspiring them to explore the world through science.

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