it is possible to use XMLHttpRequest to download pictures in static web pages. Pictures can be opened normally, but
put the web pages on the server and download them in a cross-domain way.
configured cross-domain, also used Access-Control-Expose-Headers to output some header, can be downloaded to the picture, but the downloaded picture is nearly twice the size of the original, and can not be opened, which god came out to save me, three hours did not sleep.
background code is as follows:

:

:

js :

content-length content-disposition content-typeheader
debugcontent-lengthKBlob