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Comment by robertelder | Hacker News Reader

I just updated the site to decrease the compression on the images. I took the compression level from 30 to 80 at a cost of adding about 70k to the total page size. I often try to avoid using png for any images that don't need to look really high quality because the files sizes generally seem to be larger. Having said that I don't know much about the internals of these image formats, so I suppose I should read up on them one of these days.

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The biggest reason to not use jpeg for pictures of text [1] is that as more compression is applied it discards the higher frequency components first. Text being full of thin little lines (aka high frequency changes) is one of the first things to be mangled.

A quick little test I ran was to take a screenshot of my desktop and the file sizes were:

PNG: 735k

PNG (optimized w/ pngcrush): 589k

JPEG 80: 660k (minimal artifacts, but they can be seen on inspection)

JPEG 30: 313k (text regions are starting to get muddy and take more effort to read)

JPEG 10: 163k (this is like trying to read text in a colorblindness test, lot of distracting artifacts)

On a more positive note, I enjoyed browsing your Documents folder :)

[1]: IMO screenshots should use lossless formats in general

May I ask why you don't use PNGs? For these types of screenshots I wouldn't be surprised if they ended up being smaller than the JPEGs while being lossless.

Thank you for taking the time to improve the images though, it's an interesting article nonetheless.

You were correct. I went back to do some experimenting on file sizes and I was able to update the images to .png with substantially better picture quality and a file size that was lower that the originals that had the artifacts. The page size is now about 20-30k lower than it was originally.

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