Griddy Product Images

[yatgirl]

I have an issue that I hope others have encountered and have found a solution. My cross stitch product Thumbnails pictures look 'griddy' in all internet browsers except an older version of Firefox .
I have tried all kinds of variations to make the picture from the cross stitch software: no background, photo stitch, photo diamond painting square. The full size pics look fine, but when it is automatically resized to a thumbnail, very griddy.

I tried to add an example jpg pic of this, but the forum kept saying the attachment was invalid. So I have added it via public dropbox here
https://www.dropbox.com/s/thdneild7puahdr/griddy_example.jpg?dl=0

Does anyone know what settings I can do, or how I can get a picture to resize as a 'non - griddy' thumbnail?

[DPSoftware]

The images are very regular in their construction so to resize them you would need to use an algorithm that blends colours over several pixels. Most image editors should have something but browsers probably use something much simpler so they work faster. Its better to make the image look good in an image editor and then have it displayed at that size on the website.