# What would produce this “hamburger” corruption on images?

I have an image that has gone through an unknown number of jpeg and webp conversions (at least one but more likely 2+). Currently this image is a JPEG and contains corruptions in single color or mild gradient backgrounds. What could cause this?

• Are you certain that that pattern is not present in the original image? – MBaz Mar 14 '16 at 16:09
• I suspect that the corruption is there in the original image, but that conversions back-and-forth exacerbate the issue and make the color jump in the palette table. – Peter K. Mar 14 '16 at 16:16
• I suspect you're both correct. Thanks for confirming. Getting ahold of original – duma Mar 14 '16 at 16:38
• Here's another set of photos, before corruption and after: take.ms/bfKuX – duma Mar 14 '16 at 16:58
• SE.DSP wishes you a happy new year 2017, with a kind reminding signal that your question or its answers may require some action (update, votes, acceptance, etc.) – Laurent Duval Jan 2 '17 at 22:58

JPEG projects $8\times 8$ blocks of images onto $64$ 2D cosine patterns:
The one in column $1$ and row $5$, once quantized, may look like your hamburger. Luminance and chroma components may get different subsampling patterns. I suspect that the low varying background is nearly horizontal, and due to the different processing steps, it ends up with a mid-frequency non-zero component. My main issue is its $10\times 10$ apparent size. Apparently, WebP also does some prediction on blocks.