Looking for best way to compress large maps for online VTT use

[wthrasherb]

Hello!

I'm working on a large dungeon map and it's already a large file and I'm no where near finished. It will probably be over a gig by the end of it. I've got to get it under 250 MB while retaining as much detail as possible.

I'm going to try webp first, but that's the extent of my ideas currently. I suppose once the map is finished I could cut it up into 4 parts or something then put them together in the VTT.

Anyone here have any suggestions?

[waldronate]

I'm no expert on VTTs, but I would thing that it depends on your VTT as much as anything else.
The usual file-size-reduction suggestions (reduce colors to indexed color levels, use lower compression quality, make non-critical areas solid color for better compression) may or may not be helpful depending on your specific image format and processing available. If you can identify moderate-sized blocks that are background, those areas can likely be reduced to instances of a single tiny image stretched to fill, but then you have to reassemble the image in the VTT. A similar idea is to have two layers (if allowed by your VTT) with the background texture repeating and the foreground image element(s) having a transparent background so that they might compress well.

[Tiana]

It should really be more like 10mb, for use in a VTT with decent performance. A gig is fine if that's the Photoshop file, it won't be that large when you export it as a jpg or webp. Save it at 70% quality, 70 pixels per inch, and yeah, chop it up into multiple parts if needed.

[Falconius]

Remember that VTT's are basically just browsers. No one wants to sit there for five minutes while a 250 mb picture loads and then try and move it around. Though I'm not sure why it can't be compressed to more reasonable amount anyways 150px per grid unit would be quite a lot, most are 100 or below with the average being as Tiana said 70 px per grid unit.

[Redrobes]

Not all VTTs are browsers and not all of them load all of the map as images either. And, even if all of it is based on images, then some of them reuse the same image for icon stamps so that you don't need the whole image with all occurrences of the stamped icon - just the one stamp and the locations of where they all are. So not all of them have a fixed pixels per tile value and some don't even use square tiles anyway.

So... which VTT is this big map intended for ?

[wthrasherb]

Not 150 px grid. I reduced the file size to 150 ppi from 300 ppi. The grid is only 50 px now (from 100 px). I did a test save with what I've got so far and I got it down to 28 MB, but you can't zoom in really... it's blurry now.

How do people make these complex vtt maps? My computer can't handle this. Or Photoshop can't. I don't know which one is the problem. My machine isn't new, but I've got a i7 6700 3.41 GHz with 16 GB of RAM and a SSD for a hard drive. I've dedicated 80% of my RAM to Photoshop, but this map is not playing nicely.

@Redrobes, Foundry VTT. The "map" isn't that big. I guess it was. I had the dimensions at 12,000 px x 9,000 px, but I cut it in half. The FILE SIZE is what is big. I'm trying to merge some layers to cut down on size, but it didn't help much.

I appreciate y'all taking the time to respond.

[wthrasherb]

Man, I give up. I can't even export the file now. It just gives me an error. Even after merging most of the file down from over 2 GB to 368 MB, but it's not working. This is so weird. I've never had this problem EVER. I've been using PS since like 95 or so. I've made complex maps 10,000 px x 10,000 px with no issues on this PC.

I'm open to suggestions on how to shrink the file size without loosing detail or how to increase performance with Photoshop (sorry, I know this isn't PS customer service).

[wthrasherb]

Turns out Photoshop might be broken. I'm troubleshooting now.

[selden]

Does it have to be a single image file? Might it be redesigned to consist of a relatively low resolution top-level file (I mean one that is sparse in the types of information that it shows. I don't mean using a lower-percentage jpg resolution), while containing links to more detailed regional images?

Alternatively, does it have to be a bitmapped image (jpg or png format)? Vector images (.svg format) can be much more efficient, depending on the image design.

[wthrasherb]

The files are trash and broke Photoshop. I can't do anything with them. I had to uninstall and reinstall Photoshop. I have to start over from scratch with this map. I'm going to try lower resolutions and such and see if it works better. It's just frustrating.

As for the single image file, yes. It is a dungeon and I'm not going to make each room it's own map. I could break it up somehow, but it would be less than ideal once in the VTT.

File type will be webp in the end. I will export it from photoshop as a jpg or png then convert it to webp. Vector is not an option.

Thanks for responding!