I have a photo which has a person and background.
After I open the photo in libreOffice
draw, I like to make it like the
following(1) make the photo into 2 layers. a
person is on a layer and his
background is on the other layer.(2) make the background transparent.
(3) export it png.
Can I make it into 2 layers by your help?
LibreOffice does not include a raster image manipulation tool. Use some other software, like Gimp.
It’s only possible to do that if you have a unique background which differs from foreground. Then (only then) it makes sense to knock out the image’s background in Draw (tool for that: Tools menu | color replacer).
For other proceedings use GIMP or similar program (see @mikekaganski 's answer).
@Grantler: just curious: do you know if that would work for JPG with its artifacts (I have no experience there)?
@mikekaganski : Often bad results for fotos. You can increase the percentage of replacing a specific color; say from (given) 10 % to 50 %. If you are lucky it will have the desired results. The artifacts of JPG often refuse a good replacing (this depends also on compression rate of JPG; if the rate is around 80-100 percent, the artifacts mostly are quite faint).
.
When do I use the color replacer?
I often have to scan images/graphics/diagrams out of books or I take (JPG or PNG) images from “e-books”. Then I reduce the amount of colors (that depends, 8 - 64 colors) on XnView. After having reduced the colors it is often possible to change (background) colors into white (also transparency possible). Images of 13 MB (from scanner) then have 700 kB or less space (reduced amount of colors).