Add Kotlin encoder

[hearsilent]

#41

[hearsilent]

@hangduykhiem Please review this 🙏

[hangduykhiem]

Sorry this got lost in my inbox. Will review ASAP.

[connyduck]

I tried this with the Mona Lisa and the result is not as expected 🤔

[hearsilent]

@connyduck In demo app the ratio is 20:12 (BlurHashDecoder.decode(etInput.text.toString(), 20, 12))
You should change this to your image ratio.

[connyduck]

changing the ratio only stretches the gradient

[hangduykhiem]

Yup, I tried with both config and the result is similar to Connyduck's finding. For comparison, this is the result of web encoder

And the string is LHC6SkxEElE4_JWCoyWCTIbHxsbH.

Edit: Here's one more comparison so that we can figure out where the bug is. The first one on blurha.sh decoded to LGF5]+Yk^6#M@-5c,1J5@[or[Q6, while your solution returns UEHV6nfQ2KfQg9fQfQfQkVfQaefQfQfQjtjt

[hangduykhiem]

Actually now that I think of it, @DagAgren's vision is that encode and decode are separate files that can be copy directly to the user directory.

BlurHashDecode.swift and BlurHashEncode.swift contain a decoder and encoder for BlurHash to and from UIImage. Both files are completeiy standalone, and can simply be copied into your project directly.

Can you make it so that each of them are self contained? Else I think we might need to move the whole thing to bintray or somewhere else to make it easier for others.

[hangduykhiem]

While the decoder itself is pretty much self tested @ignaciotcrespo introduced some nice test for decoder in #66 as well, I think the encoder needs some simple unit test for better verification of result.

I'm thinking of something like comparing the output of the first image with LEHV6nWB2yk8pyo0adR*.7kCMdnj and the mona lisa image with LHC6SkxEElE4_JWCoyWCTIbHxsbH. It should be easy to write and maintain, while catching the problem if we ever need to touch the encoder.

[hangduykhiem]

All being said, thank you for the PR, @hearsilent. I meant to do this a while ago, but... 😅

[hearsilent]

@connyduck @hangduykhiem I've fixed encode with wrong result. It cause by encodeAC with wrong pow method.

[hearsilent]

The result is like this:

This result is generated by BlurHashEncoder.encode(bitmap, 4, 3)

[moritzruth]

Can you please merge this? I would like to use it, but I'll use https://github.com/hsch/blurhash-java for now.