Digital Image Compression

Card Type: Technology
Difficulty: Beginner
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Description:

Image compression technologies work to minimize the file size of digital images. The three common compression formats used for images on the web are JPEG, GIF and PNG.

Purpose:

Finding the best fit compression format for an image yields the highest image quality with the smallest file size—smaller file sizes will make projects load faster.

Procedure:

  1. Open the image in the image editing tool of your choice.
  2. Save a copy of your file using the best compression format for you image and needs:
    1. JPEG: best option if you don’t need transparency or animation.
    2. GIF: used for small images or illustrative images with blocks of the same color. Supports animation and transparency.
    3. PNG: good for images with uniformly colored areas. Uses lossless compression which results in a higher quality image, but files sizes are larger. Supports transparency.
  3. Tune compression settings to the lowest acceptable quality level with optimal file size reduction.

 

Tools for working with digital images:

  • Desktop apps: Photoshop, Gimp, or iPhoto.
  • Web-based/mobile processing: Pixlr.
  • Compressors: gifsicle, jpegtran, optipng, pngquant.

Considerations:

  • Keep copies of your original uncompressed images.
  • Only compress your images once. If you need to edit an image do so on the original. Compressing an already compressed image further reduces quality.
  • If you are working on an online project, try the “Save for the Web” or “Optimize for the Web” option found in most image editing tools.

Level:

Beginner

Resources:

format-tree
Image credit: https://developers.google.com/web/fundamentals/performance/optimizing-content-efficiency/image-optimization?hl=en

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