Image compression

Picture as published

Digging deeper into OnePlus, I find they run photographic competitions, from which this picture is taken (reference 1). A little grainy, with much pixelation of the water visible if you click to enlarge, presumably the result of uploading something less than the full picture, with this one being some 200Kb compared with the Lumia's 6Mb, at least when it is not doing thumbs (reference 2).

Full zoom on the edge of the water

Zooming in, we seem to have at least two varieties of pixel, where by pixel I mean the small squares which make up the image, with each square being rather more than a just a dot of colour. The majority seem to be striped, perhaps dark one side fading to light the other (I think Powerpoint can do this sort of thing when filling one's shapes), while the minority are made up of small array of sub-pixels, perhaps seven by seven.

Other pictures on the same site seem to range up to around 1Mb and I have not noticed another one with the same sort of graininess.

No pixels

So this one looked well enough on my laptop, and even at full zoom, where one certainly loses the sharpness, there are no little squares. But then it has been compressed with YalmCo, whatever than might be.

No doubt an image processing specialist could explain what is going on here.

Reference 1: https://forums.oneplus.com/threads/shot-on-oneplus-april.1014021/page-33#post-20121483.

Reference 2: http://psmv4.blogspot.com/2019/06/fake-75.html.