Dear brothers, how is the big picture you uploaded to Mobile client compressed?

  html5, question

Dear brothers, how did you compress the big picture you uploaded to Mobile client into one that looks clear and small? I saw that the big picture of wq.jd.com inside was basically kept at 20 K, and it was also good to see their picture on the mobile phone. I don’t know how jd handled it.

The picture is reduced and the quality is reduced, thus the mobile phone screen is small and does not need so high pixels.