doc/examples-sgml/color-table.tcl (25 lines of code) (raw):
puts "<html><head>"
puts "<style>\n td { font-size: 12px; text-align: center; padding-left: 3px; padding-right: 3px}"
puts " td.bright { color: #eee; }\n td.dark { color: #222; }\n</style>"
puts "</head><body>"
puts "<table>"
# we create a 9x9 table selecting a different background for each cell
for {set i 0} { $i < 9 } {incr i} {
puts "<tr>"
for {set j 0} {$j < 9} {incr j} {
set r [expr int(255 * ($i + $j) / 16)]
set g [expr int(255 * (8 - $i + $j) / 16)]
set b [expr int(255 * ($i + 8 - $j) / 16)]
# determining the background luminosity (YIQ space of NTSC) and choosing
# the foreground color accordingly in order maintain maximum contrast
if { [expr ($r*0.29894)+($g*0.58704)+($b*0.11402)] > 128.0} {
set cssclass "dark"
} else {
set cssclass "bright"
}
puts [format "<td bgcolor=\"%02x%02x%02x\" class=\"%s\">$r $g $b</td>" $r $g $b $cssclass]
}
puts "</tr>"
}
puts "</table>"
puts "</body></html>"