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Comment by susam

2 months ago

This is going to be an odd comment, but I immediately recognised the parrot in the test images. It's the scarlet macaw from 2004 which is often used in many Wikipedia articles about colour graphics.

I think this is the original, photographed and contributed by Adrian Pingstone: https://commons.wikimedia.org/wiki/File:Parrot.red.macaw.1.a...

But this particular derivative is the one that appears most often in the Wikipedia articles: https://commons.wikimedia.org/wiki/File:RGB_24bits_palette_s...

This parrot has occurred in several articles on the web. For example, here's one article from a decade or so ago: https://retroshowcase.gr/index.php?p=palette

Parrots are often used in articles and research papers about computer graphics and I think I know almost all the parrots that have ever appeared in computing literature. This particular one must be the oldest computing literature parrot I know!

By the way, I've always been fascinated by dithering ever since I first noticed it in newspapers as a child. Here was a clever human invention that could produce rich images with so little, something I could see every day and instinctively understand how it creates the optical illusion of smooth gradients, long before I knew what it was called.

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susam

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ajb  2 months ago

The predecessor of dithering was the art of wood engraving, which reproduced the texture of illustrations in wood blocks used for printing in newspapers and books; necessarily in black and white. It's difficult to imagine now, but there was an entire industry of engravers to many of whom solely practiced engraving of others designs (often supplied drawn directly on the block to be engraved, to save time). These engravers were highly skilled and the artistry with which a piece was engraved could make a huge difference.

For example see "A treatise on wood engravings : historical and practical", by John Jackson and William Chatto, 1839[1]; here is a quote (p585 of the linked edition):

"With respect to the direction of lines, it ought at all times to be borne in mind by the wood engraver, — and more especially when the lines are not laid in by the designer, — that they should be disposed so as to denote the peculiar form of the object they are intended to represent. For instance, in the limb of a figure they ought not to run horizontally or vertically, — conveying the idea of either a flat surface or of a hard cylindrical form, — but with a gentle curvature suitable to the shape and the degree of rotundity required. A well chosen line makes a great difference in properly representing an object, when compared with one less appropriate, though more delicate. The proper disposition of lines will not only express the form required, but also produce more colour as they approach each other in approximating curves, as in the following example, and thus represent a variety of light and shade, without the necessity of introducing other lines crossing them, which ought always to be avoided in small subjects : if, however, the figures be large, it is necessary to break the hard appearance of a series of such single lines by crossing them with others more delicate."

There was even a period of a few decades after the invention of photography, during which it was not known how to mass produce photographs, and so they were manually engraved as with artworks. Eventually however, the entire profession became extinct.

[1] https://archive.org/details/treatiseonwooden00chat/page/585/.... (This is the 1881 edition)

malfist  2 months ago

This also used to be a really common test image: https://en.wikipedia.org/wiki/Lenna

But its apparently a cropped centerfold from Playboy

  • tux3  2 months ago

    The original Lenna is controversial, but I'm delighted to share the "ethically sourced Lenna": https://mortenhannemose.github.io/lena/

  • DonHopkins  2 months ago

    https://en.wikipedia.org/wiki/Grandfather_clause

    mercer on Nov 11, 2017 [–]

    Is the nipples being marked 'A' and 'B' part of the joke?

    DonHopkins on Nov 11, 2017 | parent [–]

    As far as I know, those were not the points of the joke. I noticed them for the first time yesterday too, after not noticing them for decades!

    As a teen, I'd printed it out, pinned it up on my wall next to the Cray-1 centerfold, and scribbled a bunch of modem phone numbers, user names and passwords all over it, and never even noticed.

    I did a quick search for other A's and B's and found that it used those characters as much as any other character for shading, but that sure seems like something some mischievous student, lab member, turist or sentient TECO script at the MIT-AI Lab might have done.

    There was no file security so anyone could have edited them in.

    Maybe one of Minsky's grad students was performing some A/B testing or eye tracking experiments.

    Somebody should ask RMS if EMACS had some special mode for editing line printer porn.

  • TacticalCoder  2 months ago

    And a poster of Lenna is on the wall of the Richard Hendricks character in the Silicon Valley series. Which makes sense as he's working on a compression algorithm.

quitit  2 months ago

When teaching print (halftones, LPI, CMYK etc) I also use a parrot. I've used rainbows and chameleons too, but settled on the parrot as being the most appropriate. But now I begin to wonder if I was just parroting(har har) a paradigm.