Skills: image processing work flow, matching compression level to your application Concepts: compression, visual effect of image compression, the amount of information in an image, pixilation, the importance of compression, lossy versus lossless compression This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License. Image compression

Where does this topic fit? Internet concepts – Applications – Technology – Implications Internet skills – Application development – Content creation (image) – User skills

When data types went mainstream Data typeDecade Numeric1950s Alphanumeric1960s Text1970s Image1990s Speech2000s Music2000s Video2000s HD video2010s

Image processing work flow Capture Edit Compress Distribute

Original

29% reduction

38 % reduction

50 % reduction

72 % reduction

90 % reduction

96% reduction – obvious information loss Both have the same number of pixels – explain the loss of information.

1,080,000 pixels, no information

Good enough?

Compressing with Paint.net

The big picture 65% of Internet data was images when this study was done. Is the percent greater or less today? Explain your answer.

Lossy versus lossless compression Emp. #Name Hourly rate Hours worked Gross pay 1Robinson, Jackie1040$400 2Ladd, Alan1240$480 3Douglas, Kirk5440$2,160 4Dean, James3440$1,360 5Gable, Clark1240$480 6Davis, Bette3440$1,360 7Monroe, Marylyn7640$3,040 8Williams, Ted4640$1,840 9Ruth, George4940$1,960 10Merman, Ethyl2140$840

Summary

Google image study: Google Web speed site: Speed counts: Speed counts: bin/article.cgi?f=/c/a/2010/10/03/BULB1FL2BT.DTL&ao=all Resources

1.Do you recall the steps in our image processing workflow? 2.What factors would you consider in deciding how much to compress an image? 3.Was information lost as we compressed the image? 4.The image of Lucas remained the same size by 381 pixels after we compressed it, but something changed – what changed? 5.How long will it take a user on a 100 kilobit per second link to download a 200 megabyte image? How long to download the image if it is compressed down to 100 megabytes? 6.Google found that 65% of Web traffic is images. Do you expect that to rise or fall in the future? Explain your answer. 7.As of April, 2010, the library of Congress had 167 terabytes of information online. Assuming that it is now up to 200 terabytes, and that 65% of that is images, how much storage space would they save if they could compress the images by 10% without affecting perceived quality? Self-study questions