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Ask HN: What are best ways to down res JPG images?

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Ask HN: What are best ways to down res JPG images?

#1

Post by hexeater »

Our cloud service has a ton of jpgs loaded by users. The images are loaded, then viewed occasionally by auditors and sometimes automated OCR. So written once and read/viewed ~4 times. We want to look at ways to save storage footprint, and I'd like to down sample the JPGs yet keep enough quality to keep users and automated OCR systems happy.

I'm hoping that someone has studied this problem and any pointers would be greatly appreciated.

Re: Ask HN: What are best ways to down res JPG images?

#4

Post by uberman »

For text, 8-bit indexed png or if your scans are high quality then black and white indexed png files will be hard to top.

After the downsample, run them through pngquant or advpng. The latter supports zopfli via insane mode and will likely take the longest to compress with the smallest result.

Re: Ask HN: What are best ways to down res JPG images?

#5

Post by hexeater »

uberman wrote: post #4

For text, 8-bit indexed png or if your scans are high quality then black and white indexed png files will be hard to top. After the downsample, run them through pngquant or advpng. The latter supports zopfli via insane mode and will likely take the longest to compress with the smallest result.

Thanks for suggestions. Seems like it is a standard process to convert to grey scale prior to OCR anyway. :-)
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