Posts from April 2019

The Broken Physics of “The Umbrella Academy” Finale

Published 5 months, 3 weeks ago

Not long ago, Kat and I got around to watching The Umbrella Academy’s first season on Netflix.  I thought it was pretty good!  It was a decent mix of good decisions and bad decisions by people in the story, I liked most of the characters and their portrayals, and I thought the narrative arcs came to good places. Not perfect, but good.

Except.  I have to talk about the finale, people.  I have to get into why the ending, the very last few minutes of season one, just didn’t work for me.  And in order to do that, I’m going to deploy, for the first time ever, a WordPress Spoiler Cut™ on this here blog o’ mine, because this post is spoilerrific.  Ready?  Here we go.

Massive, massive spoilers and a fair amount of science ahead!

Color Easing Isn’t Always Easy

Published 5 months, 4 weeks ago

A fairly new addition to CSS is the ability to define midpoints between two color stops in a gradient.  You can do this for both linear and radial gradients, but I’m going to stick with linear gradients in this piece, since they’re easier to show and visualize, at least for me.

The way they work is that you can define a spot on the gradient where the color that’s a halfway blend between the two color stops is located.  Take the mix of #00F (blue) with #FFF (white), for example.  The color midway through that blend is #8080FF, a pale-ish blue.  By default, that will land halfway between the two color stops.  So given linear-gradient(90deg, blue 0px, white 200px), you get #8080FF at 100 pixels.  If you use a more generic 90deg, blue, white 100%, then you get #8080FF at the 50% mark.

linear-gradient(90deg, blue, white 100%)

If you set a midpoint, though, the placement of #8080FF is set, and the rest of the gradient is altered to create a smooth progression.  linear-gradient(blue 0px, 150px, white 200px) places the midway color #8080FF at 150 pixels.  From 0 to 150 pixels is a gradient from #F00 to #8080FF, and from 150 pixels to 200 pixels is a gradient from #8080FF to #FFF.  In the following case, #8080FF is placed at the 80% mark; if the gradient is 200 pixels wide, that’s at 160 pixels.  For a 40-em gradient, that midpoint color is placed at 32em.

linear-gradient(90deg, blue, 80%, white 100%)

You might think that’s essentially two linear gradients next to each other, and that’s an understandable assumption.  For one, that’s what used to be the case.  For another, without setting midpoints, you do get linear transitions.  Take a look at the following example.  If you hover over the second gradient, it’ll switch direction from 270deg to 90deg.  Visually, there’s no difference, other than the label change.

linear-gradient(<angle>, blue, white, blue)

That works out because the easing from color stop to color stop is, in this case, linear.  That’s the case here because the easing midpoints are halfway between the color stops—if you leave them out, then they default to 50%.  In other words, linear-gradient(0deg, blue, white, blue) and linear-gradient(0deg, blue, 50%, white, 50%, blue) have the same effect.  This is because the midpoint easing algorithm is based on logarithms, and is designed to yield linear easing for a 50% midpoint.

Still, in the general case, it’s a logarithm algorithm (which I love to say out loud).  If the midpoint is anywhere other than exactly halfway between color stops, there will be non-linear easing.  More to the point, there will be non-linear, asymmetrical easing.  Hover over the second gradient in the following example, where there are midpoints set at 10% and 90%, to switch it from  270deg to 90deg, and you’ll see that it’s only a match when the direction is the same.

linear-gradient(<angle>, blue, 10%, white, 90%, blue)

This logarithmic easing is used because that’s what Photoshop does.  (Not Mosaic, for once!)  Adobe proposed adding non-linear midpoint easing to gradients, and they had an equation on hand that gave linear results in the default case.  It was also what developers would likely need to match if they got handed a Photoshop file with eased gradients in it.  So the Working Group, rather sensibly, went with it.

The downside is that under this easing regime, it’s really hard to create symmetric non-linear line gradients.  It might even be mathematically impossible, though I’m no mathematician.  Regardless, its very nature means you can’t get perfect symmetry.  This stands in contrast to cubic Bézier easing, where it’s easy to make symmetric easings as long as you know which values to swap.  And there are already defined keywords that are symmetric to each other, like ease-in and ease-out.

If you’re up for the work it takes, it’s possible to get some close visual matches to cubic Bézier easing using the logarithmic easing we have now.  With a massive assist from Tab Atkins, who wrote the JavaScript I put to use, I created a couple of CodePens to demonstrate this.  In the first, you can see that linear-gradient(90deg, blue, 66.6%, white) is pretty close to linear-gradient(90deg, blue, ease-in, white).  There’s a divergence around the 20-30% area, but it’s fairly minor.  Setting an interim color stop would probably bring it more in line.  That’s partly how I got a close match to linear-gradient(90deg, blue, ease-out, white), which came out to be linear-gradient(90deg, blue, 23%, #AFAFFF 50%, 68%, white 93%).

Those examples are all one-way, however—not symmetrical.  So I set up a second CodePen where I explored recreations of a few symmetrical non-linear gradients.  The simplest example matches linear-gradient(90deg, blue, ease-in, white, ease-out, blue) with linear-gradient(90deg, blue, 33.3%, white 50%, 61.5%, #5050FF 75%, 84%, blue 93%), and they only get more complex from there.

I should note that I make no claim I’ve found the best possible matches in my experiments.  There are probably more accurate reproductions possible, and there are probably algorithms to work out what they would be.  Instead,  I did what most authors would do, were they motivated to do this at all: I set some stops and manually tweaked midpoints until I got a close match.  My basic goal was to minimize the number of stops and midpoints, because doing so meant less work for me.

So, okay, we can recreate cubic Bézier easing with logarithmic midpoints.  Still, wouldn’t it be cool to just allow color easing using cubic Béziers?  That’s what Issue #1332 in the CSS Working Group’s Editor Drafts repository requests.  From the initial request, the idea has been debated and refined so that most of the participants seem happy with a syntax like linear-gradient(red, ease-in-out, blue).

The thing is, it’s generally not enough to have an accepted syntax—the Working Group, and more specifically browser implementors, want to see use cases.  When resources are finite, requests get prioritized.  Solving actual problems that authors face always wins over doing an arguably cool thing nobody really needs.  Which is this?  I don’t know, and neither does the Working Group.

So: if you have use cases where cubic Bézier easing for gradient color stops would make your life easier, whether it’s for drop shadows or image overlays or something I could never think of because I haven’t faced it, please add them to the GitHub issue!


Color Me FACE1E55

Published 6 months, 3 weeks ago

There’s a long history in computer programming of using hexadecimal strings that look like English words to flag errors.  These are referred to, amusingly, as “magic debug values”, and yes, Wikipedia has the lowdown.  One of the most (in)famous is DEADBEEF, which was used “on IBM systems such as the RS/6000, also used in the classic Mac OS operating systems, OPENSTEP Enterprise, and the Commodore Amiga”, among others.  It’s also become the name of a Gnu/Linux music player, and apparently does not have anything to do with Cult of the Dead Cow, at least not so far as I could determine.  Maybe someone with more knowledge can drop a comment.

Anyway, one of the things about these magic debug values is they’re usually eight characters long.  Not always, as in the case of BADC0FFEE0DDF00D (from RS/6000, again), but usually.  Nintendo used 0D15EA5E in the GameCube and Wii to indicate a normal boot (!), iOS logs DEAD10CC when an application terminates in a specific yet incorrect manner, and FEEDFACE shows up in PowerPC Mach-O binaries , as well as the VLC Player application.  Just to pick a few examples.

The eight-character nature of these magic codes has meant that, for a long time, you couldn’t also use them on the sly to define colors in CSS, because it was limited to the #RRGGBB format.  Well, those days are over.  Long over.  Eight-digit hex color values are here, have been here a while, and are widely supported.  Here are a few swatches laid over a (fully opaque) white-to-black gradient.

#abadcafe
#baaaaaaa
#deadbeef
#deadfeed
#defec8ed
#feedbacc

If you’re using Internet Explorer or Edge, those aren’t going to work for you.  At least, not until Edge switches over to Blink; then, they should work just fine.

Thanks to the way they were constructed, by only using the letters A-F, most of the colors above are mostly opaque.  The last two digits in #RRGGBBAA set the alpha channel level of the color, just like the last part of the rgba() syntax.  Thus, the EF at the end of DEADBEEF sets the alpha value to 0.937; EF is equivalent to decimal 239, and 239 ÷ 255 = 0.937 (approximately).  In other words, #DEADBEEF is essentially equivalent to rgba(222,173,190,0.937).

That’s why, of the six swatches, only the sheepish #baaaaaaa and the homophonic #feedbacc let the background gradient show through more than very slightly; their alpha channels are 0.666 and 0.8, respectively.  The rest are 0.929 and up.

Being stuck in the A-F range is fairly constraining, but that’s where hexadecimal and English overlap, so that’s how it goes.  However, if you’re willing to turn to leetspeak syntax—that is, allowing yourself to use 0 as a substitute for O, 1 for L and occasionally I, 5 for S, 7 for T, and so on—then a lot more possibilities open up.  In addition to some of the classic error codes like fee1dead (Linux), I had fun devising other eight-character color words like acc0lade and face1e55, not to mention the very nautical ccccccc5.  (Think about it.)  Behold!

#0ff1c1a1
#1337c0de
#5e1f1e55
#a114c0de
#acc01ade
#ba5e1e55
#bada55e5
#bebada55
#beefc0de
#b0bafe77
#b0a710ad
#c010ca7e
#c0de1e55
#ccccccc5
#d0d0code
#dabbad00
#dead10ad
#deadd0d0
#decea5ed
#face1e55
#fee1dead

There are still more l33t-compliant number substitutions available, like 6 for G, but I felt like I was already pushing it with the examples I have.  One could also use calculator spelling, where 9 is a stand-in for g, and even mix together l33t and calculator syntaxes in the same value.  So many possibilities!

You may have noticed one value which creates no color: #DABBAD00, which has 00 for its alpha, so it’s fully, completely transparent.  It’s fully transparent #DABBAD, I suppose, but there’s really no difference between one transparent color and another, as far as I’m concerned.  I mean, if a color falls transparent, then there’s nobody to see it, so is it really a color at all?  I say thee nay.

If you’re familiar with the way #RRGGBB hex values can be represented with the shortened #RGB syntax, then it will probably come as little surprise that #RRGGBBAA has a shortened #RGBA syntax, where each digit is duplicated.  This opens the world of four-letter words to us!  Here are a few:

#10ad
#1337
#b007
#ba5e
#bead
#beef
#c0de
#cafe
#cede
#dada
#dead
#deed
#f00d
#fade
#f8ed
#feed
#0b0e

Here, we finally have a fully opaque word-color: #BEEF expands out to #BBEEEEFF, making the alpha value FF, which decimal-translates to 255, which is fully opaque.  So we get a nice opaque powdery blue out of BEEF, which is counterintuitive in the best possible way.  Also, every time I see BBEEEEFF, either in print or in my head, I hear Mrs. Which ordering dinner.

And okay, yes, #F8ED isn’t a four-letter word, it’s a four-symbol license-plate word.  So it’s even cooler.

If you’re thinking about using these in your CSS, you might be concerned about backwards compatibility, since any browser that doesn’t understand four- or eight-digit hexadecimal color values will just drop them on the floor.  That might be okay for text coloring, since the text will likely have some color, even if it’s browser-default, which is usually black.  For backgrounds, having colors ignored probably less okay, particularly if you set foreground colors that depend on the background colors.

There are a couple of possibilities here.  One is to use the cascade and CSS error handling to your advantage, in the time-honored pattern of doing the simpler version first and the more sophisticated version second.

#example {
   color: #DEA;
   color: #DEAD;
}

That works in simple scenarios, but for more complicated situations—say, ones where you have foreground and background depending on each other—feature queries are an option to consider, if for no other reason than cleaner organization and legibility.

#example {
   color: red;
   background: #EEE;
}

@supports (color: #ABCD) {
   #example {
      color: #f00d;
      background: #feed;
   }
}

Naturally and as usual, you’ll have to figure out what makes the most sense for your situation.  Maybe the right answer will be to avoid using these sorts of values at all, although I don’t know where the fun is in that.

At any rate, I hope you’ve enjoyed this little tour of magic debug values, l33tspeak, and color words.  As always, #feedbacc is more than welcome in the comments!

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