Encoding to JPEG transfer syntaxes

[Almeida-a]

This is a first version of an implementation regarding issue #286.

It it not tested yet, however, any suggestion regarding that, or other mistakes, would be appreciated!

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Depends on #361

[Almeida-a]

Right now I just need to finish the unit tests, but since I am encountering some errors and I am still a beginner in rust, I'm taking longer to complete the rest of this pr (sorry for that); but if at any point there is a need to more quickly finish this, I can commit my work up until this point.

[Enet4]

Hey @Almeida-a, don't worry. As I intend to change the pixel data adapter API soon, it might be worth stalling this a bit more while I set up the new design, then we can work together on migrating the implementations. I hope that this works for you.

[Enet4]

Update: #361 is what I have in mind. When you have the time, please rebase this branch against it and try to adjust the implementation. Feel free to ask if you need any help.

[Enet4]

I took the liberty of rebasing this PR on top of #361 to start trying things out. I also took care of error handling in the encoder. Next I believe that this would call for a test suite to cover converting some pixel data to JPEG and back.

[Enet4]

New stuff:

• Fixed some calculations being done at u16 instead of usize, which would lead to overflow in medium/large resolutions.
• Added a test suite for writing and reading JPEG directly with adapters.

I found a few more things worth addressing at #361, but the changes to be made here should be minimal. I will take care of rebasing afterwards.

[Enet4]

@Almeida-a Can you have a look and see if the new changes make sense to you? It should hopefully be ready to merge soon.

[Almeida-a]

On it!

[Almeida-a]

Looks good, thank you for your assistance!

[Enet4]

Great! Thank you for the initiative and commitment, @Almeida-a!