I'm reading a PSD file with GIMP , now I want to save a single layer into a PNG file , but when I right click on the layer , there's no such option available.
Select the layer and copy Ctrl+C or > Edit > Copy, then Select > File > Create > From Clipboard, this creates a new document from the copied layer, or you can just make the layer you want the only thing visible.
Then select > File > Save As... then go down to "Select File Type (By Extension)" just above the help button shown here-
Then start typing png, or scroll down to find "PNG image" , or in the box where it says "All images select that box and go down to "PNG image (*.png)"
There does not seem to be an easy / automated way of accomplishing it at this time. You can, however, hold down shift and click the 'eye' next to the layer you wish to save as a PNG, this will make all other layers hidden and leave only the desired layer visible.
Then select 'File' -> 'Save As' and save as a PNG, since PNG does not support multiple layers it will ask you if you would like to merge VISIBLE layers or flatten the image -> Select 'Merge Visible Layers' and you should have a PNG of the one layer you wanted.