3 ms·

I'd call that "grayscale" rather than black and white, but interesting suggestion. I've never seen it done but looks like all sorts of things are possible: http

by theoh 11y ago

I'd call that "grayscale" rather than black and white, but interesting suggestion. I've never seen it done but looks like all sorts of things are possible: http://hodapple.com/blag/2011/11/24/obscure-features-of-jpeg.html http://hodapple.com/blag/2011/11/24/obscure-features-of-jpeg...

mzs 11y ago
Here's the Mandrill test image from SIPI and Utah as a 75% progressive JPEG with just the first scan of the most significant bit of just the DC for Y only, which is a totally expected scheme for the web back in the '90s: https://lh3.googleusercontent.com/-4tX6mfFoY4c/Vg7bg85RwcI/AAAAAAAArjY/Ze2YOUq3Q0M/s512-no/mandrill_grey.jpg https://lh3.googleusercontent.com/-4tX6mfFoY4c/Vg7bg85RwcI/A...
- theoh 11y ago
  What do you mean by "totally expected"? A Turing machine "totally expects" an infinite ribbon.
  - mzs 11y ago
    Back in the '90s I was doing work funded by DEC and later NSF with JPEG and one of the things I did was find an decent way to store them at a smaller size and resolution. I found that having the first scan be just the MSB of DC of Y and then later the MSBs of the other two DCs was the same as having the first be all three give or take two bytes over more than 90% of our corpus and it let something display in about half the time (when a 9600 baud modem was target). It's been a long time but I think what I ended-up with was first scan MSB of Y DC, next six bits of Y AC. Then MSB of Cb and Cr DC, then a scan with a few bits of Cb and Cr DC and AC and finally the rest. The idea was that for a B&W, greyscale, or color thumbnail the same JPEG would be used but only the first N scans sent followed by 0xffd9 with a width and height in the img tag. Anyway, I can't be the only one that figured-out in the days of SLIP over modems that doing this trick was a good idea.

3 ms·

I'd call that "grayscale" rather than black and white, but interesting suggestion. I've never seen it done but looks like all sorts of things are possible: http

by theoh 11y ago

mzs 11y ago
Here's the Mandrill test image from SIPI and Utah as a 75% progressive JPEG with just the first scan of the most significant bit of just the DC for Y only, which is a totally expected scheme for the web back in the '90s: https://lh3.googleusercontent.com/-4tX6mfFoY4c/Vg7bg85RwcI/AAAAAAAArjY/Ze2YOUq3Q0M/s512-no/mandrill_grey.jpg https://lh3.googleusercontent.com/-4tX6mfFoY4c/Vg7bg85RwcI/A...
- theoh 11y ago
  What do you mean by "totally expected"? A Turing machine "totally expects" an infinite ribbon.
  - mzs 11y ago
    Back in the '90s I was doing work funded by DEC and later NSF with JPEG and one of the things I did was find an decent way to store them at a smaller size and resolution. I found that having the first scan be just the MSB of DC of Y and then later the MSBs of the other two DCs was the same as having the first be all three give or take two bytes over more than 90% of our corpus and it let something display in about half the time (when a 9600 baud modem was target). It's been a long time but I think what I ended-up with was first scan MSB of Y DC, next six bits of Y AC. Then MSB of Cb and Cr DC, then a scan with a few bits of Cb and Cr DC and AC and finally the rest. The idea was that for a B&W, greyscale, or color thumbnail the same JPEG would be used but only the first N scans sent followed by 0xffd9 with a width and height in the img tag. Anyway, I can't be the only one that figured-out in the days of SLIP over modems that doing this trick was a good idea.