[evince] Evince Feature | Remove Text in Documents

[Sebastian Wiesendahl <sebastian wiesendahl de>]

Hi,

I am new around here and like to implement a feature to remove text from PDFs!


Problem:

Lately I was again confronted with the problem to remove some text in a PDF document, but I didn't find a tool to remove 
elements from a PDF with default tooling. But I was quite envy when my girlfriend showed me how easy it was with 
`preview` under macOS.

  https://askubuntu.com/questions/72920/is-there-a-better-way-to-redact-a-pdf

Best way for now seems to be, that one needs to rasterize the PDF, but I think that is unacceptable for many use cases 
and blows the document unnecessary.


Feature Proposals:
1. "Remove area":
  - Selecting an area, which removes all elements, that intersect that area with visible pixels,
    when rendered (should not remove nearby text; bounding box of a char may be within, but the actual char 
is not).
  - Should especially remove text, but also be able to remove images and any other visible elements
    (Instead of removing a whole images, may cut images into pieces and removes on the part within the area).
  - Fills the removed area with some rgba-color (default: black). The user should be able to change the color 
by
    right click on the area and change the "Area Properties" and select a color with a color picker
    (analog the "Annotation Properties...").

2. "Redact text":
  - Select text with a text cursor or select an area, when there is no text. Provides the user a text area
    (with line breaks) with the selected text (default: same font, size and gaps). Only when the user changes 
the text
    within the text area, then the actual text under the area of the selected text gets removed and will be 
replaced
    with the new text from the text area.
  - The text area should be floating on the page in edit mode and be able to be moved around with the mouse 
and
    arrow keys.


UI Preview:

  Activities   [🖹] Document Viewer ▼
  ------------------------------------------------------------
  🔖 [1| of 10] [🖊]
  ------------------------------------------------------------
  [ Note text | Highlight text | Remove area | Redact Text ]


What I need:

- Feedback on the ideas. I care about the "Remove area" feature, which should be able to censor a document 
properly.
- The "Redact text" is a nice to have, but I think a more controversial feature.

- Some help to build evince. I fooled around with meson and installed all dependencies under Ubuntu (20.04) until I 
figured that it is easier to build with the GNOME `Builder`.

- Some help integrating this feature in the right place with the proper g interfaces.
  I guess under `libdocument` as `ev-remove` and `ev-redact`. I am not a very experienced C developer.

I looking forward to your feedback!

Cheers,
Sebastian