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Command substitution into argument to convert

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Michael F. Stemper

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Jun 13, 2022, 3:28:42 PM6/13/22
to
I'm trying to time-stamp image files as they're downloaded. The
following works fine:

$ convert -pointsize 20 -fill black -draw 'text 10,20 "06/13 14:13"' RadarMap.png Stamped.png

However, hard-coding the time stamp would make it worthless. What
I really want to use is the output of:

$ date +"%m/%d %H:%M"

But no matter how I try to incorporate that into the command, I
get errors.

For instance,

$ convert -pointsize 20 -fill black -draw 'text 10,20 $(date +"%m/%d %H:%M")' RadarMap.png Stamped.png
convert: non-conforming drawing primitive definition `(' @ error/draw.c/DrawImage/3190.

or:

$ convert -pointsize 20 -fill black -draw "text 10,20 $(date +"%m/%d %H:%M")" RadarMap.png Stamped.png
convert: non-conforming drawing primitive definition `text' @ error/draw.c/DrawImage/3190.

I've even tried two steps, initializing a variable and using it:

$ ts=$(date +"%m/%d %H:%M")
$ echo $ts
06/13 14:24
$ convert -pointsize 20 -fill black -draw "text 10,20 $ts" RadarMap.png Stamped.png
convert: non-conforming drawing primitive definition `text' @ error/draw.c/DrawImage/3190.
$ convert -pointsize 20 -fill black -draw 'text 10,20 $ts' RadarMap.png Stamped.png
convert: non-conforming drawing primitive definition `ts' @ error/draw.c/DrawImage/3190.

I'm sure that what I need to do to get a dynamic argument into
convert will be obvious to everybody except me. What am I missing?

Thanks,
--
Michael F. Stemper
Deuteronomy 24:17

Michael F. Stemper

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Jun 13, 2022, 4:29:47 PM6/13/22
to
On 13/06/2022 14.28, Michael F. Stemper wrote:
> I'm trying to time-stamp image files as they're downloaded. The
> following works fine:
>
> $ convert -pointsize 20 -fill black -draw 'text 10,20 "06/13 14:13"' RadarMap.png Stamped.png
>
> However, hard-coding the time stamp would make it worthless. What
> I really want to use is the output of:
>
> $ date +"%m/%d %H:%M"
>
> But no matter how I try to incorporate that into the command, I
> get errors.


One other data point. If I try using back-quotes for the
command substitution:

$ convert -pointsize 20 -fill black -draw 'text 10,20 `date +"%m/%d %H:%M"`' RadarMap.png Stamped.png

no error message is issued, but the text that's placed on
the image is:

date +"%m/%d %H:%M"

--
Michael F. Stemper
Indians scattered on dawn's highway bleeding;
Ghosts crowd the young child's fragile eggshell mind.

Grant Taylor

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Jun 13, 2022, 6:32:27 PM6/13/22
to
On 6/13/22 1:28 PM, Michael F. Stemper wrote:
> I'm sure that what I need to do to get a dynamic argument into
> convert will be obvious to everybody except me. What am I missing?

I wonder if you are running into -- what I consider to be -- order of
operations issues related to quoting. I use the single quote around awk
statements so that the $ isn't interpreted. So there's a chance that
the $(...) inside of '...' isn't being interpreted either.

When I've run into these type of problems I usually punt to an eval
"$(date "...")" type thing and have date generate the entire command
string that is passed to eval.



--
Grant. . . .
unix || die

Lewis

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Jun 13, 2022, 8:21:05 PM6/13/22
to
In message <t88358$ad1$1...@dont-email.me> Michael F. Stemper <michael...@gmail.com> wrote:
> I'm trying to time-stamp image files as they're downloaded. The
> following works fine:

> $ convert -pointsize 20 -fill black -draw 'text 10,20 "06/13 14:13"' RadarMap.png Stamped.png

> However, hard-coding the time stamp would make it worthless. What
> I really want to use is the output of:

> $ date +"%m/%d %H:%M"

So do that.

$ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw 'text 10,20 "$MYDATE"' RadarMap.png Stamped.png

> For instance,

> $ convert -pointsize 20 -fill black -draw 'text 10,20 $(date +"%m/%d %H:%M")' RadarMap.png Stamped.png

Notice that you have changed the quotes since you have "" inside '' in
your original. You would need to figure out the escaping to make this
right. Setting a variable avoids this.


> $ convert -pointsize 20 -fill black -draw "text 10,20 $(date +"%m/%d %H:%M")" RadarMap.png Stamped.png

same issue, you are not quoting the way the original command is quoted.


> I've even tried two steps, initializing a variable and using it:

> $ ts=$(date +"%m/%d %H:%M")
> $ echo $ts
> 06/13 14:24
> $ convert -pointsize 20 -fill black -draw "text 10,20 $ts" RadarMap.png Stamped.png

Your original line has 'text 10,20 "the date is here"'

Note the quotes.

--
I presume you're mortal, and may err.

Michael F. Stemper

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Jun 14, 2022, 8:59:30 AM6/14/22
to
On 13/06/2022 19.21, Lewis wrote:
> In message <t88358$ad1$1...@dont-email.me> Michael F. Stemper <michael...@gmail.com> wrote:
>> I'm trying to time-stamp image files as they're downloaded. The
>> following works fine:
>
>> $ convert -pointsize 20 -fill black -draw 'text 10,20 "06/13 14:13"' RadarMap.png Stamped.png
>
>> However, hard-coding the time stamp would make it worthless. What
>> I really want to use is the output of:
>
>> $ date +"%m/%d %H:%M"
>
> So do that.
>
> $ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw 'text 10,20 "$MYDATE"' RadarMap.png Stamped.png

No error message is given. The text drawn on the image is:
$MYDATE

>
>> For instance,
>
>> $ convert -pointsize 20 -fill black -draw 'text 10,20 $(date +"%m/%d %H:%M")' RadarMap.png Stamped.png
>
> Notice that you have changed the quotes since you have "" inside '' in
> your original. You would need to figure out the escaping to make this
> right. Setting a variable avoids this.
>
>
>> $ convert -pointsize 20 -fill black -draw "text 10,20 $(date +"%m/%d %H:%M")" RadarMap.png Stamped.png
>
> same issue, you are not quoting the way the original command is quoted.

This is true. I have tried several different ways of quoting. None
of them have worked for me.

>> I've even tried two steps, initializing a variable and using it:
>
>> $ ts=$(date +"%m/%d %H:%M")
>> $ echo $ts
>> 06/13 14:24
>> $ convert -pointsize 20 -fill black -draw "text 10,20 $ts" RadarMap.png Stamped.png
>
> Your original line has 'text 10,20 "the date is here"'
>
> Note the quotes.

And when I put single quotes around the text directive, I get:

$ ts=$(date +"%m/%d %H:%M")
$ convert -pointsize 20 -fill black -draw 'text 10,20 $ts' RadarMap.png Stamped.png
convert: non-conforming drawing primitive definition `ts' @ error/draw.c/DrawImage/3190.
$


--
Michael F. Stemper
A preposition is something you should never end a sentence with.

Lewis

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Jun 14, 2022, 4:26:18 PM6/14/22
to
In message <t8a0ng$umi$1...@dont-email.me> Michael F. Stemper <michael...@gmail.com> wrote:
> On 13/06/2022 19.21, Lewis wrote:
>> In message <t88358$ad1$1...@dont-email.me> Michael F. Stemper <michael...@gmail.com> wrote:
>>> I'm trying to time-stamp image files as they're downloaded. The
>>> following works fine:
>>
>>> $ convert -pointsize 20 -fill black -draw 'text 10,20 "06/13 14:13"' RadarMap.png Stamped.png
>>
>>> However, hard-coding the time stamp would make it worthless. What
>>> I really want to use is the output of:
>>
>>> $ date +"%m/%d %H:%M"
>>
>> So do that.
>>
>> $ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw 'text 10,20 "$MYDATE"' RadarMap.png Stamped.png

> No error message is given. The text drawn on the image is:
> $MYDATE

Then it is still a quoting issue, probably beaus you hav single quotes
around the outside. I do not use the convert tool, so I can’t tell you
specifically what the issue is, but the first thing I wold do is
eliminate the single quotes, assuming they are not required by convert.


$ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw "text 10,20 $MYDATE" RadarMap.png Stamped.png

or maybe

$ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw "text 10,20 \"$MYDATE\"" RadarMap.png Stamped.png

Remember that ' and " ae very different, and ' do not usually allow
expansion of variables contained inside, but sometimes it is hard to
know when a variable is being expanded by the shell and when it is being
passed to the command.

Either way, sometimes you just have to play with the quotes and the
escapes.

--
Were it not for frustration and humiliation I suppose the human race
would get ideas above its station. -Ogden Nash

Lewis

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Jun 14, 2022, 7:38:35 PM6/14/22
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In message <slrntahrn9....@m1mini.local> Lewis <g.k...@kreme.dont-email.me> wrote:
> $ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw "text 10,20 \"$MYDATE\"" RadarMap.png Stamped.png

This works:

MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill white -draw "text 10,20 \"$MYDATE\"" image.jpg image-date.jpg

I expect this also works, but did not try:
convert -pointsize 20 -fill white -draw "text 10,20 \"$(date +"%m/%d %H:%M")\"" image.jpg image-date.jpg

This SHOULD work because the $() should protect the "" inside...

(of course, this draws white text no matter what, which is fine if the
image is dark, but invisible if the top left is white).

--
The "H" in Jesus H Christ comes from "Harold be Thy name" in the
Lord's Prayer.

Michael F. Stemper

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Jun 15, 2022, 8:55:29 AM6/15/22
to
On 14/06/2022 18.38, Lewis wrote:
> In message <slrntahrn9....@m1mini.local> Lewis <g.k...@kreme.dont-email.me> wrote:
>> $ MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill black -draw "text 10,20 \"$MYDATE\"" RadarMap.png Stamped.png
>
> This works:
>
> MYDATE=$(date +"%m/%d %H:%M");convert -pointsize 20 -fill white -draw "text 10,20 \"$MYDATE\"" image.jpg image-date.jpg
>
> I expect this also works, but did not try:
> convert -pointsize 20 -fill white -draw "text 10,20 \"$(date +"%m/%d %H:%M")\"" image.jpg image-date.jpg

Those both work. Thanks.

I had tried various permutations of single and double quotes, but
never thought of escaping them.

--
Michael F. Stemper
This email is to be read by its intended recipient only. Any other party
reading is required by the EULA to send me $500.00.
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