Does Obscelis detect faces?
Not in this version. Faces, handwritten signatures and stamps are masked with a zone you draw; the zone is painted black in the copy like any other mask.
Guide
How to redact an image or a screenshot
A photo of a document, a screenshot or a scan can show far more than intended, and carry more than it shows. Here is how to mask what it shows and remove what it carries.
Updated
In short
- Mask with opaque black, not with a blur or pixels.
- Remove the metadata: location, date, device, sometimes a thumbnail of the original.
- Save a new file rather than editing the original in place.
- Check the copy at full size, and check its properties.
Blur and pixels are not enough
A blur or a mosaic keeps part of the information: pixelated text can sometimes be read back by trying candidate texts until one gives the same pixels, and a face or a number stays recognisable to someone who already suspects it. An opaque black area leaves nothing to work with.
Draw the mask a little larger than what it hides, so that no edge of a letter stays visible.
What an image carries without showing it
Besides its pixels, an image file can hold metadata:
- the GPS position where the photo was taken;
- the date and time, and the make and model of the phone or camera;
- the software that edited it, and sometimes a smaller copy of the original image;
- comments and descriptions added by an application.
Screenshots and crops
Cropping or painting over a screenshot in an editor does not always rewrite the whole file. In 2023, flaws in the screenshot editor of some phones and in a Windows capture tool left the cropped part recoverable from the saved file. Export a new file from a tool that writes every pixel again, rather than saving over the capture.
Redacting an image with Obscelis
Import a PNG, JPEG, TIFF, GIF, BMP or WebP image. Obscelis reads the text in it with on-device OCR, in French and English, and proposes the names, e-mail addresses, phone numbers, IBANs and identifiers it finds. Faces, signatures and stamps are not detected automatically in this version: draw a zone over them. Each page of a TIFF and each frame of a GIF is a page of its own.
The copy keeps the format of the source. Masked areas are painted opaque black, every frame is written again, and the EXIF, GPS, XMP and colour-profile metadata and comments are always removed. Obscelis then decodes the copy on its own, checks that every masked area is black and that no metadata is left, and only then publishes it.
Everything happens on your computer: the picture is never sent to a service.
Questions
Does the image lose quality?
A PNG, TIFF or WebP copy keeps every pixel outside the masks. A JPEG copy is encoded again at a high quality, so it loses a little, as any JPEG does when it is saved again.
Can I redact a photo taken with an iPhone?
HEIC photos are not read yet. Export the photo as JPEG, or set the camera to Most Compatible in the iPhone settings, then import it.
Other guides
How to redact a Word document permanently
A black highlight in Word hides a word on screen and leaves it in the file. Here is where a Word document keeps information, how to remove it, and how to check the copy.
Anonymising CVs for blind recruitment
Reading an application without the name, the photo or the address keeps attention on experience and skills. Here is what to mask, what to keep and how to organise it.
How to redact a PDF permanently
Redacting a PDF means removing information from the file, not hiding it on screen. Here is the method, the traps, and how to check the result.
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