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Draw a Tk Canvas using Ordnance Survey data
this example from a Well House Consultants training course
Source code: osmap.tk Module: M200
set reftab {{0 0 SV SW SX SY SZ TV} {100 100 SR SS ST SU TQ TR} {100 200 SM SN SO SP TL TM} {200 300 SH SJ SK TF TG} {200 400 SC SD SE TA} {100 500 NW NX NY NZ OV} {100 600 NR NS NT NU GX} {0 700 NL NM NN NO} {0 800 NF NG NH NJ NK} {0 900 NA NB NC ND} {100 1000 HW HX HY HZ} {300 1100 HT HU} {400 1200 HP}} proc convert from { global reftab regexp (..)(...)(...) $from all let east north regsub "^0{1,2}" $east "" east regsub "^0{1,2}" $north "" north foreach row $reftab { for {set col 2} {$col < [llength $row]} {incr col} { if {[lindex $row $col] == $let} { set nbase [lindex $row 1] set ebase [lindex $row 1] set retnorth [expr $nbase * 10 + $north] set reteast [expr ($ebase + 100 * ($col -2))*10 + $east] return "$reteast $retnorth" } } } return 0 } proc propn {left right steps stepno} { return [expr int($left + ($right - $left) / $steps. * $stepno)] } proc cvt from { global leftbase topbase global gridwid gridhei global canwid canhei set gridit [convert $from] set easting [expr ([lindex $gridit 0] - $leftbase) * $canwid / $gridwid ] set northing [expr ($topbase - [lindex $gridit 1]) * $canhei / $gridhei ] return "$easting $northing" } set topleft ST730950 set bottomright SU344171 set tlpoint [convert $topleft] set brpoint [convert $bottomright] set leftbase [lindex $tlpoint 0] set topbase [lindex $tlpoint 1] set gridwid [expr [lindex $brpoint 0] - [lindex $tlpoint 0]] set gridhei [expr [lindex $tlpoint 1] - [lindex $brpoint 1]] set canhei 700 set canwid [expr int($canhei. * $gridwid / $gridhei)] proc plot from { global pixwid pixcol set type [lindex $from 0] set os 2 switch $type { join { set start [cvt [lindex $from 1]] set to [cvt [lindex $from 2]] set steps [expr [lindex $from 3] / 3] .wiltshire create line [lindex $start 0] [lindex $start 1] \ [lindex $to 0] [lindex $to 1] \ -width $pixwid -fill $pixcol for {set k 0} {$k<=$steps} {incr k} { set xc [propn [lindex $start 0] \ [lindex $to 0] $steps $k] set yc [propn [lindex $start 1] \ [lindex $to 1] $steps $k] set xl [expr $xc + $os] set yl [expr $yc + $os] set xr [expr $xc - $os] set yr [expr $yc - $os] .wiltshire create oval \ $xl $yl $xr $yr \ -fill black } } place { set gridref [lindex $from 1] set wording [lrange $from 2 end] set placement [cvt $gridref] .wiltshire create text \ [lindex $placement 0] [lindex $placement 1] \ -anchor w -text " $wording"} width { set pixwid [lindex $from 1] } color { set pixcol [lindex $from 1] } } } canvas .wiltshire -width $canwid -height $canhei -background white pack .wiltshire set fhx [open tracks.txt r] set pixwid 1 set pixcol black while {[gets $fhx here] > -1} { plot $here } Learn about this subject
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