Three years ago I played a bit with bar charts.
I started a YouTube channel and I like to create some bar charts.
An example is:
#!/usr/bin/env tclsh

package require Tk
package require BLT

package require sqlite3

set viewsArr {}
set weekArr {}

sqlite3 db ~/Databases/youtube.sqlite
db eval {
SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
, SUM(dayViews) AS WeekTotals
FROM dayViews
WHERE WeekNo > '37'
GROUP BY WeekNo
ORDER BY WeekNo
} {
lappend viewsArr ${WeekTotals}
lappend weekArr ${WeekNo}
}
db close

blt::barchart .bc -plotbackground black
.bc axis configure y -stepsize 100
.bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
pack .bc -side top -expand yes -fill both

This gives a window with the bar chart. I can make a screen dump
of-course, but is there a way to also write the bar chart to a PNG
file?

What is a good resource for learning to work with Tk, (bar) charts and
the like?

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

Look for pdf4tcl: https://sourceforge.net/projects/pdf4tcl/

You can either recode the drawing code to create a PDF bargraph, or just
convert the canvas to PDF.

Note: natively, Tcl can export a canvas to a PostScript file ($canvas
postscript ...). There are utilities to convert PostScript to PDF or PNG
(GhostScript can do that).

And I believe the TkImg package can convert a canvas to an image, which could
then be saved as a PNG file.

At Sat, 21 Oct 2023 14:30:10 +0200 Cecil Westerhof <Cecil@decebal.nl> wrote:

>
> Three years ago I played a bit with bar charts.
> I started a YouTube channel and I like to create some bar charts.
> An example is:
> #!/usr/bin/env tclsh
>
>
> package require Tk
> package require BLT
>
> package require sqlite3
>
>
> set viewsArr {}
> set weekArr {}
>
> sqlite3 db ~/Databases/youtube.sqlite
> db eval {
> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
> , SUM(dayViews) AS WeekTotals
> FROM dayViews
> WHERE WeekNo > '37'
> GROUP BY WeekNo
> ORDER BY WeekNo
> } {
> lappend viewsArr ${WeekTotals}
> lappend weekArr ${WeekNo}
> }
> db close
>
> blt::barchart .bc -plotbackground black
> .bc axis configure y -stepsize 100
> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
> pack .bc -side top -expand yes -fill both
>
> This gives a window with the bar chart. I can make a screen dump
> of-course, but is there a way to also write the bar chart to a PNG
> file?
>
>
> What is a good resource for learning to work with Tk, (bar) charts and
> the like?
>

--
Robert Heller -- Cell: 413-658-7953 GV: 978-633-5364
Deepwoods Software -- Custom Software Services
http://www.deepsoft.com/ -- Linux Administration Services
heller@deepsoft.com -- Webhosting Services

Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 14:44:10 UTC+2:
> Three years ago I played a bit with bar charts.
> I started a YouTube channel and I like to create some bar charts.
> An example is:
> #!/usr/bin/env tclsh
>
>
> package require Tk
> package require BLT
>
> package require sqlite3
>
>
> set viewsArr {}
> set weekArr {}
>
> sqlite3 db ~/Databases/youtube.sqlite
> db eval {
> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
> , SUM(dayViews) AS WeekTotals
> FROM dayViews
> WHERE WeekNo > '37'
> GROUP BY WeekNo
> ORDER BY WeekNo
> } {
> lappend viewsArr ${WeekTotals}
> lappend weekArr ${WeekNo}
> }
> db close
>
> blt::barchart .bc -plotbackground black
> .bc axis configure y -stepsize 100
> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
> pack .bc -side top -expand yes -fill both
>
> This gives a window with the bar chart. I can make a screen dump
> of-course, but is there a way to also write the bar chart to a PNG
> file?
>
>
> What is a good resource for learning to work with Tk, (bar) charts and
> the like?
>
> --
> Cecil Westerhof
> Senior Software Engineer
> LinkedIn: http://www.linkedin.com/in/cecilwesterhof

slides.pdf
https://blt.sourceforge.net/

https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript

and
https://wiki.tcl-lang.org/page/BLT

debian 12 with blt and blt-demo

greg <gregor.ebbing@googlemail.com> writes:

> Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 14:44:10 UTC+2:
>> Three years ago I played a bit with bar charts.
>> I started a YouTube channel and I like to create some bar charts.
>> An example is:
>> #!/usr/bin/env tclsh
>>
>>
>> package require Tk
>> package require BLT
>>
>> package require sqlite3
>>
>>
>> set viewsArr {}
>> set weekArr {}
>>
>> sqlite3 db ~/Databases/youtube.sqlite
>> db eval {
>> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
>> , SUM(dayViews) AS WeekTotals
>> FROM dayViews
>> WHERE WeekNo > '37'
>> GROUP BY WeekNo
>> ORDER BY WeekNo
>> } {
>> lappend viewsArr ${WeekTotals}
>> lappend weekArr ${WeekNo}
>> }
>> db close
>>
>> blt::barchart .bc -plotbackground black
>> .bc axis configure y -stepsize 100
>> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
>> pack .bc -side top -expand yes -fill both
>>
>> This gives a window with the bar chart. I can make a screen dump
>> of-course, but is there a way to also write the bar chart to a PNG
>> file?
>>
>>
>> What is a good resource for learning to work with Tk, (bar) charts and
>> the like?
>
>
>
> slides.pdf
> https://blt.sourceforge.net/
>
> https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript" rel="nofollow" target="_blank">https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript
>
> and
> https://wiki.tcl-lang.org/page/BLT

At the moment I use:
.bc postscript configure -landscape yes -maxpect yes
.bc postscript output ytWeek.ps

And I convert it to png with:
gs -dSAFER -o ytWeek.png ytWeek.ps

Works reasonable, but there is a problem: left and right there is a
transparency area of 135 pixels and above and under of 95 pixels.
How do I get rid of this area?

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 22:28:25 UTC+2:
> greg writes:
>
> > Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 14:44:10 UTC+2:
> >> Three years ago I played a bit with bar charts.
> >> I started a YouTube channel and I like to create some bar charts.
> >> An example is:
> >> #!/usr/bin/env tclsh
> >>
> >>
> >> package require Tk
> >> package require BLT
> >>
> >> package require sqlite3
> >>
> >>
> >> set viewsArr {}
> >> set weekArr {}
> >>
> >> sqlite3 db ~/Databases/youtube.sqlite
> >> db eval {
> >> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
> >> , SUM(dayViews) AS WeekTotals
> >> FROM dayViews
> >> WHERE WeekNo > '37'
> >> GROUP BY WeekNo
> >> ORDER BY WeekNo
> >> } {
> >> lappend viewsArr ${WeekTotals}
> >> lappend weekArr ${WeekNo}
> >> }
> >> db close
> >>
> >> blt::barchart .bc -plotbackground black
> >> .bc axis configure y -stepsize 100
> >> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
> >> pack .bc -side top -expand yes -fill both
> >>
> >> This gives a window with the bar chart. I can make a screen dump
> >> of-course, but is there a way to also write the bar chart to a PNG
> >> file?
> >>
> >>
> >> What is a good resource for learning to work with Tk, (bar) charts and
> >> the like?
> >
> >
> >
> > slides.pdf
> > https://blt.sourceforge.net/
> >
> > https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript" rel="nofollow" target="_blank">https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript
> >
> > and
> > https://wiki.tcl-lang.org/page/BLT
> At the moment I use:
> .bc postscript configure -landscape yes -maxpect yes
> .bc postscript output ytWeek.ps
>
> And I convert it to png with:
> gs -dSAFER -o ytWeek.png ytWeek.ps
>
> Works reasonable, but there is a problem: left and right there is a
> transparency area of 135 pixels and above and under of 95 pixels.
> How do I get rid of this area?
> --
> Cecil Westerhof
> Senior Software Engineer
> LinkedIn: http://www.linkedin.com/in/cecilwesterhof

https://manpages.debian.org/testing/blt-dev/blt::graph.3tcl.en.html

Finally, to get hardcopy of the graph, use the postscript component.
# Print the graph into file "file.ps"

..g postscript output file.ps -maxpect yes -decorations no

This generates a file file.ps containing the encapsulated PostScript of the graph. The option -maxpect says to scale the plot to the size of the page. Turning off the -decorations option denotes that no borders or color backgrounds should be drawn (i.e. the background of the margins, legend, and plotting area will be white).

At Sat, 21 Oct 2023 22:17:34 +0200 Cecil Westerhof <Cecil@decebal.nl> wrote:

>
> greg <gregor.ebbing@googlemail.com> writes:
>
> > Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 14:44:10 UTC+2:
> >> Three years ago I played a bit with bar charts.
> >> I started a YouTube channel and I like to create some bar charts.
> >> An example is:
> >> #!/usr/bin/env tclsh
> >>
> >>
> >> package require Tk
> >> package require BLT
> >>
> >> package require sqlite3
> >>
> >>
> >> set viewsArr {}
> >> set weekArr {}
> >>
> >> sqlite3 db ~/Databases/youtube.sqlite
> >> db eval {
> >> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
> >> , SUM(dayViews) AS WeekTotals
> >> FROM dayViews
> >> WHERE WeekNo > '37'
> >> GROUP BY WeekNo
> >> ORDER BY WeekNo
> >> } {
> >> lappend viewsArr ${WeekTotals}
> >> lappend weekArr ${WeekNo}
> >> }
> >> db close
> >>
> >> blt::barchart .bc -plotbackground black
> >> .bc axis configure y -stepsize 100
> >> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
> >> pack .bc -side top -expand yes -fill both
> >>
> >> This gives a window with the bar chart. I can make a screen dump
> >> of-course, but is there a way to also write the bar chart to a PNG
> >> file?
> >>
> >>
> >> What is a good resource for learning to work with Tk, (bar) charts and
> >> the like?
> >
> >
> >
> > slides.pdf
> > https://blt.sourceforge.net/
> >
> > https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript" rel="nofollow" target="_blank">https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript
> >
> > and
> > https://wiki.tcl-lang.org/page/BLT
>
> At the moment I use:
> .bc postscript configure -landscape yes -maxpect yes
> .bc postscript output ytWeek.ps
>
> And I convert it to png with:
> gs -dSAFER -o ytWeek.png ytWeek.ps
>
> Works reasonable, but there is a problem: left and right there is a
> transparency area of 135 pixels and above and under of 95 pixels.
> How do I get rid of this area?

GhostScript is probably creating a "page" (eg 8.5" x 11") and is filling out
the "empty" "paper". You probably need to set the paper size to match the
image (or something like that). I wonder if ImageMagick will take care of
that...

sudo apt install imagemagick

>

--
Robert Heller -- Cell: 413-658-7953 GV: 978-633-5364
Deepwoods Software -- Custom Software Services
http://www.deepsoft.com/ -- Linux Administration Services
heller@deepsoft.com -- Webhosting Services

Cecil Westerhof <Cecil@decebal.nl> writes:

> greg <gregor.ebbing@googlemail.com> writes:
>
>> Cecil Westerhof schrieb am Samstag, 21. Oktober 2023 um 14:44:10 UTC+2:
>>> Three years ago I played a bit with bar charts.
>>> I started a YouTube channel and I like to create some bar charts.
>>> An example is:
>>> #!/usr/bin/env tclsh
>>>
>>>
>>> package require Tk
>>> package require BLT
>>>
>>> package require sqlite3
>>>
>>>
>>> set viewsArr {}
>>> set weekArr {}
>>>
>>> sqlite3 db ~/Databases/youtube.sqlite
>>> db eval {
>>> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
>>> , SUM(dayViews) AS WeekTotals
>>> FROM dayViews
>>> WHERE WeekNo > '37'
>>> GROUP BY WeekNo
>>> ORDER BY WeekNo
>>> } {
>>> lappend viewsArr ${WeekTotals}
>>> lappend weekArr ${WeekNo}
>>> }
>>> db close
>>>
>>> blt::barchart .bc -plotbackground black
>>> .bc axis configure y -stepsize 100
>>> .bc element create best -xdata ${weekArr} -ydata ${viewsArr} -label {}
>>> pack .bc -side top -expand yes -fill both
>>>
>>> This gives a window with the bar chart. I can make a screen dump
>>> of-course, but is there a way to also write the bar chart to a PNG
>>> file?
>>>
>>>
>>> What is a good resource for learning to work with Tk, (bar) charts and
>>> the like?
>>
>>
>>
>> slides.pdf
>> https://blt.sourceforge.net/
>>
>> https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript" rel="nofollow" target="_blank">https://wiki.tcl-lang.org/page/BLT+%2D+graph+%2D+printing+postscript
>>
>> and
>> https://wiki.tcl-lang.org/page/BLT
>
> At the moment I use:
> .bc postscript configure -landscape yes -maxpect yes
> .bc postscript output ytWeek.ps
>
> And I convert it to png with:
> gs -dSAFER -o ytWeek.png ytWeek.ps
>
> Works reasonable, but there is a problem: left and right there is a
> transparency area of 135 pixels and above and under of 95 pixels.
> How do I get rid of this area?

By using convert from Image Magick:
convert -trim -resize 800x ytWeek.ps ytWeek.png

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

On Sat, 21 Oct 2023 14:30:10 +0200
Cecil Westerhof <Cecil@decebal.nl> wrote:

> Three years ago I played a bit with bar charts.
> I started a YouTube channel and I like to create some bar charts.
> An example is:
> #!/usr/bin/env tclsh
>
>
> package require Tk
> package require BLT
>
> package require sqlite3
>
>
> set viewsArr {}
> set weekArr {}
>
> sqlite3 db ~/Databases/youtube.sqlite
> db eval {
> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
> , SUM(dayViews) AS WeekTotals
> FROM dayViews
> WHERE WeekNo > '37'
> GROUP BY WeekNo
> ORDER BY WeekNo
> } {
> lappend viewsArr ${WeekTotals}
> lappend weekArr ${WeekNo}
> }
> db close
>
> blt::barchart .bc -plotbackground black
> .bc axis configure y -stepsize 100
> .bc element create best -xdata ${weekArr} -ydata ${viewsArr}
> -label {} pack .bc -side top -expand yes -fill both
>
> This gives a window with the bar chart. I can make a screen dump
> of-course, but is there a way to also write the bar chart to a PNG
> file?
>

Yes. I tested this on Ubuntu 18 with package tk8.6-blt2.5, which gives
BLT version 2.5.3.

# Create a image to hold the graph, use the "snap" subcommand and then
# write the image to a file.
image create photo snapshot
..bc snap snapshot
snapshot write snapshot.png -format png

>
> What is a good resource for learning to work with Tk, (bar) charts and
> the like?
>

Tcl.

I didn't have your database as a data set, so the expr function can
quickly generate data sets based upon any function you can imagine -

# Sample graph data generator.
proc grfunc {x} {
set xr [expr $x * 3.14159 / 180]
return [expr sin($xr) + 4 * cos($xr)]
}

set xseries ""
set yseries ""
set xstep 5

for {set x 0} {$x < 360} {incr x $xstep} {
lappend xseries $x
lappend yseries [grfunc $x]
}

blt::barchart .bc -plotbackground black
..bc axis configure y -stepsize 100
..bc element create best -xdata $xseries -ydata $yseries \
-label {} -barwidth $xstep
pack .bc -side top -expand yes -fill both

Kind regards,
Scott

--

Scott Pitcher <scotty@svptechnicalservices.com.au> writes:

> On Sat, 21 Oct 2023 14:30:10 +0200
> Cecil Westerhof <Cecil@decebal.nl> wrote:
>
>> Three years ago I played a bit with bar charts.
>> I started a YouTube channel and I like to create some bar charts.
>> An example is:
>> #!/usr/bin/env tclsh
>>
>>
>> package require Tk
>> package require BLT
>>
>> package require sqlite3
>>
>>
>> set viewsArr {}
>> set weekArr {}
>>
>> sqlite3 db ~/Databases/youtube.sqlite
>> db eval {
>> SELECT strftime('%W', dayDate, '+1 day') AS WeekNo
>> , SUM(dayViews) AS WeekTotals
>> FROM dayViews
>> WHERE WeekNo > '37'
>> GROUP BY WeekNo
>> ORDER BY WeekNo
>> } {
>> lappend viewsArr ${WeekTotals}
>> lappend weekArr ${WeekNo}
>> }
>> db close
>>
>> blt::barchart .bc -plotbackground black
>> .bc axis configure y -stepsize 100
>> .bc element create best -xdata ${weekArr} -ydata ${viewsArr}
>> -label {} pack .bc -side top -expand yes -fill both
>>
>> This gives a window with the bar chart. I can make a screen dump
>> of-course, but is there a way to also write the bar chart to a PNG
>> file?
>>
>
> Yes. I tested this on Ubuntu 18 with package tk8.6-blt2.5, which gives
> BLT version 2.5.3.
>
> # Create a image to hold the graph, use the "snap" subcommand and then
> # write the image to a file.
> image create photo snapshot
> .bc snap snapshot
> snapshot write snapshot.png -format png

Works likes a charm.
Thanks.

Now I have to learn to get the most out of it. ;-)

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof

Cecil Westerhof <Cecil@decebal.nl> writes:

>> Yes. I tested this on Ubuntu 18 with package tk8.6-blt2.5, which gives
>> BLT version 2.5.3.
>>
>> # Create a image to hold the graph, use the "snap" subcommand and then
>> # write the image to a file.
>> image create photo snapshot
>> .bc snap snapshot
>> snapshot write snapshot.png -format png
>
> Works likes a charm.
> Thanks.
>
> Now I have to learn to get the most out of it. ;-)

By the way the generated PNG is a lot smaller as the one generated
with the postscript/ghostscript way and at the same time looks a lot
better.
It is also less steps, so a very BIG win.

--
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof