No. The covered pixels are overwritten before the file is saved, so the original values aren't in the file at all.

Why not just blur it?

Text under a weak blur or small pixels can sometimes be recovered. A solid box leaves nothing to recover.

Is the rest of the image changed?

PNGs stay lossless. JPGs and WebPs are re-encoded at high quality, so there's a tiny change you won't see.

No. Everything runs on your device, which is what you want for private material.

Redact image

Hide private details with solid boxes that really replace the pixels.

Runs on your device. Nothing is uploaded.