[OT] JPEG + graphs == hideous [LWN.net]

[OT] JPEG + graphs == hideous

Posted Jan 11, 2008 5:35 UTC (Fri) by PaulMcKenney (subscriber, #9624)
In reply to: [OT] JPEG + graphs == hideous by roelofs
Parent article: What is RCU? Part 2: Usage

Well, there certainly still are geographies where the bandwidth is quite restricted, so I cannot complain.

For xfig, how about this .gif, as opposed to the six-times-bigger .jpg?

For gnuplot, how about this .gif, as opposed to the nine-times-bigger .jpg?

Now I just have to remember to cut-and-paste from the right set of scripts for next time!

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[OT] JPEG + graphs == hideous

Posted Jan 11, 2008 6:42 UTC (Fri) by roelofs (guest, #2599) [Link]

For xfig, how about this .gif, as opposed to the six-times-bigger .jpg?

Indeed--and notice how the red dashed line is so much brighter now, and the black-on-green text is far sharper? JPEG hates sharp boundaries. (Gibbs' phenomenon and all.)

For gnuplot, how about this .gif, as opposed to the nine-times-bigger .jpg?

You (or gnuplot) must have used a very high quality setting for the JPEG, because that nine-times-bigger JPEG is actually grayscale (i.e., nominally one-third the raw data, or at least one-half given the usual YCbCr subsampling of the color channels in a three-component JPEG). Indeed, it's so high-quality that it has only four gray shades in it (two white, two black) and is visibly flawless even to my eye.

Just for jollies, I converted your images to PNG (gif2png -s rwlock*.gif) and then ran them through pngcrush (pngcrush -brute -e -crb.png -rem alla rwlock*.png). Here are the results:

 44965 Jan 10 21:13 rwlockRCUupdate.jpg             // 24-bit, 504 x 350 (xfig)
  7266 Jan 10 21:10 rwlockRCUupdate.gif             // 3-bit palette
  3350 Jan 10 22:13 rwlockRCUupdate.png             // 4-bit palette (gif2png)
  2867 Jan 10 22:13 rwlockRCUupdate-crb.png         // 4-bit palette (pngcrush)

 45664 Jan 10 21:22 rwlockRCUperfwtPREEMPT.jpg      // 8-bit, 640 x 480 (gnuplot)
  4940 Jan 10 21:22 rwlockRCUperfwtPREEMPT.gif      // 1-bit palette
  3326 Jan 10 22:13 rwlockRCUperfwtPREEMPT.png      // 1-bit grayscale (gif2png)
  2967 Jan 10 22:13 rwlockRCUperfwtPREEMPT-crb.png  // 1-bit grayscale (pngcrush)

In short, more than a factor of 15 smaller than the JPEGs, yet perfect quality. (These are the kinds of images for which PNG was designed.)

Greg