feat: add pixelate and pseudo-pixelate

[RobertMueller2]

Closes: #90
builds on #600 and #555 because it doesn't make sense otherwise
I think the commits are a bit of a mess now, but it'll get better when the prereqs are merged.

This implements a pixelate tool with two modes

• regular mode with a normal block pixelation, this is, depending on selected area and image resolution, reversible
• "independent mode" or pseudo-pixelate that takes data from outside the selected area and applies distance weighting. The original area is entirely overwritten by the interpolated data. Then, the regular pixelation function creates a block-pixelate look from this.

Some things are still open:

• figure out a better icon - help needed please. for both pixelate and pseudo-pixelate
• reach out to flameshot guys regarding credits
• double check if south and east buffers aren't actually off by one
• figure out if BLOCKSIZE is good at a value of 32. This may actually need to be adjustable. Follows size+annotation-size-factor now. Annotation-size-factor gets rounded to 1, S is 4, M is 8, L is 16. These values may need some fine tuning in the future.
• find a user friendly solution for "selected area too small to pixelate". Shows different colours for rectangle now. But perhaps needs more conditions, e.g. when there's no fringe, the pixelation can fail as well.
• alt is probably not a good way to switch between pixelate and pseudo-pixelate, it's inconsistent with other tools. implement as variant mode on top of refactor: use custom component for tool buttons to allow grouping #600. Now removed in favour of distinct tool entries.
• indicate editing consistent with feat: indicate active editing in toolbar #444
• add redact mode - perhaps we can take into account the luminance of the surrounding area and switch between black and white.
• result depends on scaling, this bug was copied from blur (also see Blur result depends on scaling #602)

Known limitations:

• in pseudo-pixelate mode, canvas background may contribute to the mix of pixels if the selection is started at image origin
• in pseudo-pixelate mode, if the selection "leaves" Satty's window, nothing happens. We would be lacking one fringe in that instance.

This PR was inspired by

• https://github.com/flameshot-org/flameshot/pull/3765/changes
• [needs a human pls] add pixelate functionalty (on alt) to blur #468 by kikeijuu (superseded by this PR)

Regarding the credits, the idea with taking "fringes" was taken from said PR, but I reimplemented the gist of it according to my understanding. I did, for example, skip any additional noise which might be suitable for adding later. Also, actually iterating the source (fringes) and target data (overwritten area) works a bit different due to the objects used. I don't think we need to talk about a separate licence for this bit, but we'll see what the flameshot guys say about this.

pixelation2.mp4

[RobertMueller2]

for brighter images, the "independent mode" result is a bit too bright. Maybe the weighting math isn't great yet.

EDIT: need to divide everything by two if I have a a horizontal and a vertical influence, they each add to 1. that looks a lot better. Unfortunately, now I have to redo the recording.

[RobertMueller2]

Perhaps we also really need to call this "pseudo-pixelate", no need to re-invent lingo? 😉

[robertwidfen]

Regarding the icon, maybe "checkerboard"?

But I like "eye-off-regular" better as it fits more into the existing icons.

Also I see a small issue if the pixelate region is a the border and covers less than one "pixel" in width/height it will not pixelate anything.

[RobertMueller2]

Also I see a small issue if the pixelate region is a the border and covers less than one "pixel" in width/height it will not pixelate anything.

yup, I noticed that too while using/testing this locally, at the very least it needs some indication whether the selected area is big enough or not. That'll need some rework, i'll place this in draft mode for now.

[pointydev]

Hey there, just came across this pull and noticed the following in the OP:

• figure out if BLOCKSIZE is good at a value of 32. This may actually need to be adjustable.

On Flameshot this is handled using the scrollwheel to change tool size (also the case for the rest of the sized tools, such as line width, etc). I personally use a tool size of 2 on most occasions, equating to 6px blocks for me:

Adjustable block size would be highly appreciated as it can help emphasise that an area is meant to be pixelated in a final image, depending on the scale of the surrounding elements.

[robertwidfen]

Thank you for sharing this. Personally I do not switch the tool size much, but I like the idea for blur and pixelate, there the S-M-L might not be sufficient. Pixelate so far does not take S-M-L into account.

I was also thinking about integrating pixelate into the existing blur tool to avoid adding another toolbar button. But currently we have no concept of tool individual styles, which might be handy to switch between blur/pixelate, add double arrow, switch rounded rectangle on/off, etc.

[RobertMueller2]

I would tie it to S-M-L and annotation size factor, and a static modifier, which is from top of my head what the other tools do. I wouldn't add a scroll wheel logic specifically for this -- but the scroll wheel does work on the annotation size, so at least there's that. ;)

[RobertMueller2]

I was also thinking about integrating pixelate into the existing blur tool to avoid adding another toolbar button. But currently we have no concept of tool individual styles, which might be handy to switch between blur/pixelate, add double arrow, switch rounded rectangle on/off, etc.

If such a concept was ready to use, I might add this to the blur tool. But actually coming up with a concept and discussing it, I think we should open a separate issue :)