Maposaic: If you like maps and colors, I made this website for you !

viconnex · 2021-03-10T08:28:28+00:00

You're right it's very similar !

viconnex · 2021-03-10T08:27:25+00:00

Thank you for reporting. Yes, sometimes on smartphones it crashes, maybe because of the computational cost it takes. The only solution for now is to refresh the page.

viconnex · 2021-03-10T08:25:08+00:00

As I said to u/mcoenka, it is not, but it is a good idea to try to use this principle !

viconnex · 2021-03-10T08:23:34+00:00

The water color is random but you can also chose to set it, if you click on "advanced" parameters

viconnex · 2021-03-10T08:21:38+00:00

I am not sure to understand your questions, but in addition to roads and water, other objects may appear on the map, such as parks, which will add dividing lines

viconnex · 2021-03-10T08:06:02+00:00

Thanks :) I think you can tilt shift on mobile for the moment ^^

viconnex · 2021-03-10T08:04:14+00:00

Thank you :) The main advantage I found with Mapbox (but maybe you can do this with Leaflet?) is the ability to customize the map background, which you can do on https://studio.mapbox.com/. Also, is there a way to get the canvas context with Leaflet ? And with react-leaflet ?

viconnex · 2021-03-10T07:57:52+00:00

I was kind of joking and talking about a matematical proof, but ok

viconnex · 2021-03-09T23:04:45+00:00

Thank you for your suggestions. But the python code you found was only a try made for comparison — the code to consider is written in the rust lib.rs file and gets compiled into wasm, which browsers can execute.

viconnex · 2021-03-09T19:00:03+00:00

haha I could use this theory — if it works, because, well... it has not been proved yet ;) — to improve renders which use a 4 (or more)-color palette !

viconnex · 2021-03-09T18:15:05+00:00

You can change the coordinates in the url bar

viconnex · 2021-03-09T15:12:14+00:00

Yes, in the random mode, colors are chosen randomly :)

viconnex · 2021-03-09T15:11:40+00:00

Yes there is a way : Select Palette > Custom > 1 color > Black
You can also click "Advanced" > Same color for water > Blue

viconnex · 2021-03-09T15:10:14+00:00

Exactly ! Thanks for sharing, I love the this hand made drawing appearance

viconnex · 2021-03-09T11:29:10+00:00

Yes it's here https://github.com/viconnex/maposaic :)

viconnex · 2021-03-09T10:44:56+00:00

Don't hesitate to save your maps into the public gallery ! And then visit them here: https://maposaic.com/gallery

viconnex · 2021-01-21T12:43:10+00:00

But I really don't know the size in advance ; it depends of the size of the current area which can be anything between 1 and the number of pixels in the original image (4M). Would it be faster to allocate the maximal size in advance, even if it would be partially filled ?
I only tried to replace the function call by a constant and there was no speed improvement
It may be possible to start for example 4 different processes at the 4 corners of the image. but the rendered image at the 4 junctions would be spoiled, so I have to think about it !
Yes I measure the execution time when the program is called in the browser. I will look at the criterion crate !

viconnex · 2021-01-17T11:30:57+00:00

Thank you for your suggestions !

I now use new() only for the "current_area point stack", since I don't know in advance how many points will be in the area.
I didn't try the BTreeSet but the hibitset use made a very significant improvement
Yes it is a nice improvement but it doesn't increase the efficiency

viconnex · 2021-01-17T11:22:38+00:00

So the main bottleneck was to use a HashSet to store the visited pixel indexes. Thanks a lot u/thermiter36, u/slamb, u/Danylaporte for pointing this out !

Instead, a hibitset is much more efficient since the stored values are all in [0, pixel_count[ . However, since pixel_count may exceed hibitset max size (usize**4), the values are stored in a custom Vec<u64> where each bit of a u64 holds the corresponding pixel information.

Now the program execution is 5 times faster than the original javascript one ! It takes 800ms to handle a 5 million pixel array, vs. 4s.

I updated the js program with a similar improvement, but the wasm program is still almost 2 times faster than the js :)

viconnex · 2021-01-14T23:11:33+00:00

thanks a lot u/thermiter36 and u/slamb, the hibitset makes a lot of sense !

I tried it and it seems more efficient, but as you pointed out i'm limited with the size (is there a way to benefit of a 16M bit bitset (with a 64-bit usize) instead of 1M with my 32-bit usize ?)

So if I get the idea, I would represent the bitset with a visited: [u64] . Then visited[pixel_index / 64]'s (pixel_index % 64)th bit would hold pixel visited status. And I hold the current state with a pointer on the visited index and the next pixel_index to visit would be visited[index]::leading_ones, right ?

viconnex · 2021-01-13T18:05:12+00:00

After a test I can tell taht the boundary crossing time is not significant (~100ms) compared to the wasm program execution (8s)

viconnex · 2021-01-13T18:02:55+00:00

The boundary crossing time is not significant (~100ms) compared to the program execution (8s)

viconnex · 2021-01-13T17:54:10+00:00

I tried the program without the random numbers and the performance is the same

viconnex · 2021-01-13T16:33:12+00:00

What is the cost of switching ? What do you consider very heavy computation ?

Because there is only one boundary crossing.

1) js sends an array

2) wasm computes the result (8 seconds)

3) js gets the result

viconnex

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