On Image Compression

This image has been removed due to threats on my life.

Compressing pictures for internet display is no easy task. On the web two formats are used predominately, just because that is how it started. GIF, which is was used by CompuServ and now is being charged for in a ridiculous case of evilness that I won’t get in to here, and JPEG, which is the Joint Picture Experts Group standard for still image compression. JPEG is for photos and pretty pictures, while GIF is best for things with few colors. GIF keeps file sizes small on items that are more simplistic, say the “AgBlog” logo on top of this page. It is stored as 2 GIF images because that makes the file sizes really tiny. Whereas the picture of me on top with the little word bubble, that is JPEG, because it has more colors and is more complex and thusly must be compressed in a better way.

So here is something I just discovered: Selective compression with JPEGs. Assuming your browser supports it, you should see a picture of my good friend Sophie sticking out her tongue. Now this picture was taken in bad lighting conditions and is a pretty awful example of good photography. That also means it doesn’t compress well. Putting this photo on the web with full quality it would be about 62 kilobytes, and with your average 56k modem that would take 12 seconds in ideal circumstances, and more frequently, much longer. So I had to compress Sophie.

This usually means you have to lower the quality of the whole image. But when I do that, the tongue thrust is not clearly visible. The solution is selective compression! I compress and smooth most of the picture, except for a box around Sophie’s head that is at a higher quality. Can you see it? Neat, huh?

And if you haven’t yet seen right through this as an attempt to give legitimacy to the posting of an unflattering picture under the guise of a life lesson, you have now been told. Isn’t it great how the people I like most I make fun of most often?