Task #20918 (Improve PNG filesize on save)

[Bujacikk]

Hi, I was working on task: #20918

I little changed Save method for 8bbp, 24bbp and alpha channel. I hope it is good. I added DeflaterOutputStream with max compression.
I add some unit tests too. I know it was not in the task, but I am doing it as a school task and we had to add some tests, so I hope It is not a big problem. If it is, I can remove them.

PS: I am sorry for git messages. I read conditions too late.

[RoosterDragon]

Extra unit tests are great, no issues with that.

For the commits, you might find the following useful to condense your changes into a single commit, and for updating the commit message. We would usually ask that the commit message is something that describes the change.

• https://stackoverflow.com/questions/5189560/how-do-i-squash-my-last-n-commits-together
• https://stackoverflow.com/questions/179123/how-to-modify-existing-unpushed-commit-messages

As both of those questions note, you will need to force push those changes, so that your PR is updated.

Thanks for your contribution.

[Bujacikk]

Extra unit tests are great, no issues with that.

For the commits, you might find the following useful to condense your changes into a single commit, and for updating the commit message. We would usually ask that the commit message is something that describes the change.

• https://stackoverflow.com/questions/5189560/how-do-i-squash-my-last-n-commits-together
• https://stackoverflow.com/questions/179123/how-to-modify-existing-unpushed-commit-messages

As both of those questions note, you will need to force push those changes, so that your PR is updated.

Thanks for your contribution.

Done

[abcdefg30]

Code changes seem simple enough. 👍 Some minor/style nits.

[PunkPun]

Ping, should the PR be taken over?

[PunkPun]

Force pushed fixes to style violations. LGTM

[PunkPun]

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