Your formats jfif & png are image formats not related to aiff. (Your link is to aiff
discussion).
JFIF is like JPEG or JPG. It can be opened in basic viewer programs in
most computers.
While onscreen copy to clipboard by means of 'prt screen' key (Windows etc.).
On Macintosh press Cmd-shift-4 to enclose any rectangle and create your png.
I have used Irfanview for 25 yrs. Others like Gimp.
Save as any image format in any size or resolution by variable compression or target image size.
I like to enlarge the pixel size x2 then reduce file size to 10%
eg. 750 pix square reduced to 50 kbytes .jpg or 396k .png with best quality
You can >image> sharpen , >auto-adjust, manual >color corrections, and do lots of cool tricks. Also can use Adobe filters.
just want to add:
* use .JPG for photos (where almost every pixel has a different color)
* use .PNG for graphs, screenshots and so on (where a lot of pixels have identical color. Like lines, or background)
Irfanview is so easy to use paste / save as, but I get lazy. You can simply delete the image and insert the thumbnail too. PNG 68k
But using the save AS JPG option allows yout to use any compression with a sliding scale or set the target size like JPG 50k but then when recopied from browser is a 1.57 MB image. This is 30:1 compression but takes a bunch of extra steps