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

[Paul Rowe]

Hi Bruce,
I don't think there's an option. I had a similar case where I had an old
paper-based map that my map connected to. I ended up scaling and rotating
the background image of the old map until it was right. I used the maximum
jpg compression to reduce the size of the enlarged image, but it would be
useful to have size/rotation options for background images.

A similar case is placing images on a generated PDF map. I can't see a way
to size/rotate these, but this would be really useful.

Thanks,
Paul

On Fri, 7 May 2021 at 08:14, Bruce Mutton <bruce at tomo.co.nz> wrote:

> 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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