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

Fri May 7 00:09:58 CEST 2021

Hi Bruce,

I have had reason to digitise some 2 point plan sketches and then stitch them together, I know it wouldn’t be ideal, but could you build up the picture like this in a sub folder then export a new .th2 for the full area of the cave that you need, so life is easier in the future.

Ie separate scraps for each background image, then when the .th2 has been exported, you can manipulate the scraps to your desired parts of the cave?

Al
Ps loving getting back to being underground again :)

> On 6 May 2021, at 22:07, Paul Rowe <armchair.caver.nz at gmail.com> wrote:
> 
> 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.
>> 
>>  
>> 
>>  
>> 
>> 
>> 
>> <image004.png>
>> 
>>  
>> 
>> 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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