Skip to main content

Converting Between Colour Formats: hex, 8-bit, 16-bit and float.

The gnocl package has its own C-based conversion commands but here are the pure Tcl equivalents.

 

 

# !/bin/sh
# the next line restarts using tclsh \
exec tclsh "$0" "$@"
package require Gnocl
# colour in hexadecimal
set clr #8B6914
puts $clr
proc hex2rgb { hex {opt -8bit} } {
    if { [lsearch "-8bit -16bit -float" $opt] == -1 } {
        set msg "Error. Wrong option $opt.\nValid options are: -8bit (default) -16bit, or -float."
        return -code error $msg
    }
    # convert to 8bit values
    scan $hex "#%02x%02x%02x" r g b
    switch $opt {
        -16bit {
            # convert to 0-65535
            if {$r eq 0} {set r 0} {set r [expr int ( ($r.0/255)*65535 )]}
            if {$g eq 0} {set g 0} {set g [expr int ( ($g.0/255)*65535 )]}
            if {$b eq 0} {set b 0} {set b [expr int ( ($b.0/255)*65535 )]}
            }
        -float {
            # convert 0-1.0
            if {$r eq 0} {set r 0.0} {set r [expr $r.0/255]}
            if {$g eq 0} {set g 0.0} {set g [expr $g.0/255]}
            if {$b eq 0} {set b 0.0} {set b [expr $b.0/255]}
            }
    }
    return [list $r $g $b]
}
puts [hex2rgb $clr]
puts [hex2rgb $clr -16bit]
puts [hex2rgb $clr -float]
proc rgb2hex { clr {opt -8bit} } {
    lassign $clr r g b
    if { [lsearch "-8bit -16bit -float" $opt] == -1 } {
        set msg "Error. Wrong option $opt.\nValid options are: -8bit (default) -16bit, or -float."
        return -code error $msg
    }
    switch $opt {
        -16bit {
            # convert to 0-65535
            set d [expr 255.0/65535]
            if {$r eq 0} {set r 0} {set r [expr int ( $r.0*$d )]}
            if {$g eq 0} {set g 0} {set g [expr int ( $g.0*$d )]}
            if {$b eq 0} {set b 0} {set b [expr int ( $b.0*$d )]}
            }
        -float {
            # convert 0-1.0
            if {$r eq 0} {set r 0} {set r [expr int ( $r*255.0 )]}
            if {$g eq 0} {set g 0} {set g [expr int ( $g*255.0 )]}
            if {$b eq 0} {set b 0} {set b [expr int ( $b*255.0 )]}
            }
    }
    return [format "#%02X%02X%02X" $r $g $b]
}
puts [rgb2hex {139 105 20} ]
puts [rgb2hex {35723 26985 5140} -16bit]
puts [rgb2hex {0.5450980392156862 0.4117647058823529 0.0784313725490196} -float]
proc rgba2hex { clr {opt -8bit} } {
    lassign $clr r g b a
    if { [lsearch "-8bit -16bit -float" $opt] == -1 } {
        set msg "Error. Wrong option $opt.\nValid options are: -8bit (default) -16bit, or -float."
        return -code error $msg
    }
    switch $opt {
        -16bit {
            # convert to 0-65535
            if {$a == ""} {set a 65535}
            set d [expr 255.0/65535]
            if {$r eq 0} {set r 0} {set r [expr int ( $r.0*$d )]}
            if {$g eq 0} {set g 0} {set g [expr int ( $g.0*$d )]}
            if {$b eq 0} {set b 0} {set b [expr int ( $b.0*$d )]}
            if {$a eq 0} {set a 0} {set a [expr int ( $a.0*$d )]}
            }
        -float {
            # convert 0-1.0
            if {$a == ""} {set a 1.0}
            if {$r eq 0} {set r 0} {set r [expr int ( $r*255.0 )]}
            if {$g eq 0} {set g 0} {set g [expr int ( $g*255.0 )]}
            if {$b eq 0} {set b 0} {set b [expr int ( $b*255.0 )]}
            if {$a eq 0} {set a 0} {set a [expr int ( $a*255.0 )]}
            }
        default {
            if {$a == ""} {set a 255}
            }
    }
    return [format "#%02X%02X%02X%02X" $r $g $b $a]
}
puts [rgba2hex {255 255 255}]
puts [rgba2hex {255 255 255 255}]

 

Comments

Post a Comment

Popular posts from this blog

gnocl::calendar

Given this module some attention today. Added some of the more package wide options to the module and created customised handler for setting the month. (For some odd reason months are are counted 0-11 whereas days are 1-31.) There's still a little more to do to this one including the addition of code to store diary details. Here's the working test script to show the range of options at work. The percentage substitution string item %e explores something that I've been toying with, the name of the signal/event that initiated the call. Ok, a script can keep its own internal trace but who knows, it might prove useful. #--------------- # calendarTest.tcl #--------------- # Author:   William J Giddings # Date:     07/05/09 #--------------- #!/bin/sh # the next line restarts using tclsh \ exec tclsh "$0" "$@" #--------------- package require Gnocl set cal [gnocl::calendar] $cal configure -day 8 -month 7 -year 1956 $cal configure -rowHeight 1 -colWidth 1 $ca...
7 comments
Read more

Gnocl Dashboard

Over the past few programming sessions I've been working on producing a central point, a dashboard, around which it's possible to see the various Gnocl widgets and commands in operation. In many ways like the demo script which shipped with the earlier releases of Gnocl but offers much more. The introspection functionality provides details of the various options and sub-commands of each Gnocl procedure which are displayed under the associated tab. Sample scripts are included for each item which offers newcomers a clearer insight into how make the most of what's on offer.
6 comments
Read more

Getting Widget Style Properties

Until the move over to Gtk4, Gnocl is still built against the Gtk 2.21 libraries. One of the inconveniences of Gtk is getting and setting widget style settings which are considered to be set globally by the desktop style settings and not for the programmer to tinker around with. Needless to say, there are times when different defaults are preferred, largely to draw the users attention to 'something a bit different'. The function gtk_widget_modify_font  is a convenience function to set the widget basefont as shown in this snippet from the button.c module,  if ( options[baseFontIdx].status == GNOCL_STATUS_CHANGED ) { GtkWidget *label; label = gnoclFindChild ( GTK_WIDGET ( para->button ), GTK_TYPE_LABEL ); PangoFontDescription *font_desc = pango_font_description_from_string ( Tcl_GetString ( options[baseFontIdx].val.obj ) ); gtk_widget_modify_font ( GTK_WIDGET ( label ), font_desc ); pango_font_description_free ( font_desc ); } Unfortunately, there's no d...
Post a Comment
Read more