[Therion] XTherion background image control and bitmap file size question

[Bruce Mutton]

Mōrena

I am wondering if XTherion can scale background images, or if anyone has
hints on scanned image settings that generate a larger background image,
that is economical on bytes?

 

Back story:

I created a multi-level survey (shaft system in cave) with PocketTopo,
rather than creating many small survey files to keep each level separate.

At home I printed the PocketTopo bitmap, then sketched over three of the
four main levels that I now want to draw with Therion.

Then I created an xvi with TopParser (I chose my usual export settings, and
of course maybe I could have chosen better settings).

 

You can see the xvi and some drawing directly on that xvi in the image
below.

You can also see the three 100 dpi png background images that I imported
into XTherion.

The three images are much smaller than the xvi and while it so happens the
zoom range is such in XTherion that I could easily draw my scraps over them,
I would like all four scrap background to be a similar size.  It just makes
life easier into the future that way.

I am a novice when it comes to bitmap manipulation, but I managed to use
GIMP to scale up one of the images about 3.5 times.  You can also see that
in the image below.  It is about the same size as the xvi which is what I am
after 

 

My frustration is that the original png images are all about 600 kB and the
enlarged image is about 3000 kB.  I am a miser and I would like to minimise
bloat in my project repository.

 

Can we scale the image in XTherion, using the original smaller file as the
permanent source?

Or are there tricks to enlarging the png image while maintaining a modest
file size?

I am aware that jpg will likely compress to fewer bytes, and will try that
unless it becomes too blurry.

 

 





 

It looks like XTherion th2 file header has some unused controls. I could not
find any documentation on this, so I have deduced the format as follows…

 

##XTHERION## xth_me_image_insert {x coord visibility[0=off, 1=on] gamma} {y
coord {<unknown empty variable>}} filename and path <unknown 0 variable> {<
unknown empty variable >}

 

Maybe there is scope for scaling and rotation of images by XTherion in here?
!!

 

Sample of th2 file header

 

##XTHERION## xth_me_image_insert {1386.4418110200002 1 1.0}
{844.5244881899999 7.14} ptopo/7-Laghu_p.xvi 0 {}

##XTHERION## xth_me_image_insert {1893.842519685 1 1.0} {1306.5748031498001
7.19} ptopo/9-Laghu_p.xvi 0 {}

##XTHERION## xth_me_image_insert {1278.0 1 1.0} {585.8818897638002 {}}
ptopo/7-LaghuPLAN-Sketches-26Jul2020-Pg01of03.png 0 {}

##XTHERION## xth_me_image_insert {550.0 1 1.0} {589.8818897638002 {}}
ptopo/7-LaghuPLAN-Sketches-26Jul2020-Pg02of03.png 0 {}

##XTHERION## xth_me_image_insert {6.0 1 1.0} {583.8818897638002 {}}
ptopo/7-LaghuPLAN-Sketches-26Jul2020-Pg03of03.png 0 {}

##XTHERION## xth_me_image_insert {2568.0 0 0.7943282347242815}
{1891.8818897638002 {}} ptopo/7-LaghuPLAN-Sketches-26Jul2020-Pg01of03B.png 0
{}

 

Thanks for any insights.

Regards

Bruce

 

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