I think there was a thread on this back in July/August in "I may be stupid...".
My method is a bit different, and uses Adobe Photoshop Business edition as the picture editor, 'cos it happens to be on my computer.
If you happen to have Photoshop, open up the picture in this, > advanced > size > Photo size > then you can 'change width' (yours are 3.05cm) to 20 cm, and 'change resolution' from 2 or 300 to 72 pixels per inch. Save file as JPEG. Close file, then re-open your picture file (not in Photshop) to check that file size is less than 265kb. If it is not, go back into Photoshop and change resolution to something smaller (say, 50 pixels per inch).
That's my way, but then I do stick oilers into petrol trucks (which is why I have to remain anonymous) :whistle: :-D :-D