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Busy Background Breaks Bulletin

Question: With text overlapping a picture of a person with a black-and-white-striped shirt. No matter what fixed "color value" you choose or what system you express it in (RGBA, APCA, etc.), you're going to have some of your letterforms appear in an area of insufficient contrast. (e.g. if you choose a dark color, your letters won't be readable on top of the black shirt stripe and visa versa for a light color).

Spatially Simplifing Stressful Stripes

Funny you should mention this. One of the experiments that we use in the lab for determining the middle point of perceptual contrast, specifically involves putting text against stripes of black and white.

The spatial frequency, in other words the size of the stripes relative to the font, is substantially important. As is the overall size and weight of the font. If I understand what you are asking for — maximum contrast at any given point, the results may not be what you expect. Here are examples.

Text on B&W

Phi Alternate Expression

The formula for phi can be reduced to a positive exponent, multiplication, and addition:

$$\begin{align} \phi = 5^{0.5} \times 0.5 + 0.5 \end{align}$$

This is clear and easy to remember, demonstrates interesting relationships, and is less obtuse than the formula as usually written. This can also improve computational efficiency (of admittedly marginal importance). Here is an example for javascript:

BRINTNESS

Fast integer lightness calculations from RGB — by Andrew Somers

brintness is an integer brightness/lightness/darkness calculation

This is part of an experiment in estimating a perceived brightness while remaining in integer math and using bitshifts to maximize performance (avoiding all subtraction, division, and square-root calculations).

The Issue

The traditional means to determine the perceived lightness or brightness for a given color value is to first normalize R, G, and B from 0-255 to 0.0-1.0, linearize the values via exponent or more exotic methods (we assume colors are in a gamma encoded color space, such as sRGB), and then after linearizing, creating a linear luminance value by applying coefficients to each of the R, G, B values, adding them, and then finally applying an exponent or more exotic math to find a predicted lightness value.

	// An object of Kelly's 22 colors, converted from rjurney's array
	// Color names are camelCase, and 'ish' was removed from all
	// The two-name colors have an alternate name as well, such as:
	// example: orangeYellow lightOrange manilla is "#e1a11a"
	// As for "maximum contrast", I do not endorse that claim

	// theory - https://eleanormaclure.files.wordpress.com/2011/03/colour-coding.pdf (page 5)
	// kelly's colors - https://i.kinja-img.com/gawker-media/image/upload/1015680494325093012.JPG
	// hex values - http://hackerspace.kinja.com/iscc-nbs-number-hex-r-g-b-263-f2f3f4-242-243-244-267-22-1665795040

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	BBEdit / BBEdit-Lite / TextWrangler Regular Expression Guide Modified: 2018/08/10 01:19
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	NOTES:

	The PCRE engine (Perl Compatible Regular Expressions) is what BBEdit and TextWrangler use.

	Items I'm unsure of are marked '# PCRE?'. The list while fairly comprehensive is not complete.