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This is it. Let’s say you’re covering a red pixel with a black pixel. There’s no way that red pixel will in any way “survive JPEG compression” because the comp
by laudecum 4y ago
This is it.
Let’s say you’re covering a red pixel with a black pixel. There’s no way that red pixel will in any way “survive JPEG compression” because the compression happens on the raw pixel data; the raw pixel data no longer has a red pixel.
- ummonk 4y agoIf the red pixel affected the encoding of nearby pixels in the compressed original, which you've now neglected to redact, then the data very well could persist.
- BoorishBears 4y agoThat's not the point the other posts are making. They're saying that before encoding the red dot could have been X pixels wide, and to the naked eye it would seem that after encoding it's still only X pixels wide... but due to compression artifacts it may now actually be affecting an area X+Y pixels wide. So only covering X pixels could leak Y pixels of information. It honestly sounds a bit paranoid to me, but it's definitely possible.
- addaon 4y ago> Let’s say you’re covering a red pixel with a black pixel. There’s no way that red pixel will in any way “survive JPEG compression” because the compression happens on the raw pixel data; the raw pixel data no longer has a red pixel. This is trivially untrue for JPEG; JPEG often stores chroma info as 4:2:0, that is at a quarter the resolution of luminance info. In this common case, covering a single red pixel in the decoded form only removes a quarter of the chroma information from its presence (and this is easy to not notice if, for example, the other three pixels that share its chrominance are nearly black).
- laudecum 4y ago