Blacking out

A black rectangle drawn over words does not remove them. In an ordinary PDF application the box is painted over the text, and the text is still in the file: still selectable, still searchable, still there for anyone who scripts the document. That is how court filings and classified papers have leaked, over and over.

So blacking out here is two separate acts: saying what should go, and then making a copy from which it has gone.

First: say what should go

Legal ▸ Black Out (⇧⌘B) places a black rectangle. Nothing is removed yet. The rectangle can be moved, resized, recoloured and deleted like any other mark, and it is in the marks list like any other mark.

It works on either of two things:

• a rectangle you have dragged out with the region tool, or
• the text you have selected, which gives one rectangle per line, so a passage over three lines becomes three marks that follow the words rather than one box covering everything between them.

You can also turn a shape already on the page into a black-out: select it and choose Legal ▸ Make This a Black-Out. Any shape of any colour will do. With a mixed selection, whichever way most of them are set, all of them go the other way. The same item reads Stop Being a Black-Out over a shape that already is one, and turns it back into an ordinary shape.

A black-out has to be declared rather than recognised by its colour. A white rectangle on a white page is invisible and still has to remove what is under it; a black highlight or a fill at ninety-nine per cent looks like a removal and is not one. Removing is a kind of mark, not a colour.

What a black-out looks like

Declaring a shape a black-out makes it opaque. A swatch normally draws at a quarter opacity, and a see-through black-out would show the very words it is meant to take away. Declared, the shape is painted solid in its own colour, outline and fill alike. Undeclared again, it gets its translucency back.

Second: make it so

The removal happens when you make the copy. See Making marks permanent, and read it before using either command, because two commands there look alike and are not:

A reader who takes the first for the second has published what they meant to hide.

What "removes" means

The page is taken apart, not painted over. Its drawing commands are read, and the ones that put anything under a black-out are not written to the new file: text, vectors and all. A picture under a black-out is decoded, the covered pixels painted out, and the picture written back, so those pixels stop existing at the picture's own resolution. Everything else on the page is written as the bytes it already was.

It removes the shape, not the box around it. An oval takes what is inside the oval; a diagonal line takes a band along the line, not the far corners of the rectangle it spans.

The page is not turned into an image. That would remove the text, the vectors and the fonts of the whole page along with the passage. A page that cannot be filtered honestly is refused, and nothing is written.

When it is burnt in, a black-out is painted in its own colour, so the finished page matches the one you approved. A white patch over scanner noise stays a white patch. A colour that cannot be read as red, green and blue falls back to black.

Undo

Marking is undoable. Applying is not, in any copy that has left this application. That is why the two acts are separate.

Reasons

A black-out can carry a reason for why the passage was taken out. The reason is kept in a private key, not as a note another reader's application would show: knowing that a box hides personal data rather than commercially confidential material narrows what is under it. It stays in this working document across saves; the permanent copy carries no reasons.

Saving with black-outs still unapplied

Saving a document that still carries a black-out that has not been applied raises a warning:

1 black-out mark(s) have not been applied. Saving keeps them as marks: the pages look right, and what is under them is still in the file for anyone who selects, searches or scripts it. File ▸ Make Marks Permanent removes it - until then this document is not redacted.

with Save Anyway and Make Marks Permanent… to choose between.

Watch: a short video for this page is still to come.

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