Hank,
Adding to what Cacophonix said...
First, right click on the photo a few post above this one and choose "Properties". You will see the web site it came from, but more important, Dimensions. 400x266 is probably the smallest,, but for line drawing would probably want 700x900 or so - readable without overwhelming the screen and still a small file.
That said, I personally use photobucket (didn't like Google's picassa as seemed like wanted to take over all photos on my computer and I uninstalled it). Photobucket is free, upload the photo then use the edit function to resize it. Caution, when resized down, can't resize up and have to re-upload the original if you resize too small. The nice thing about photobucket, it gives you a choice of 4 variations of the photo address for intended use. In this case, choose the "img" variation and a straight paste into the reply. All the "insert image" icon does in the reply area is insert the "img" tags and you are supposed to past the unaltered/straight photoaddress (first of the 4 choices in photobucket) between the two "img" tags.
Disadvantage? By design, this forum does not download the photo to its server but reads by active link. Delete the photo or close the photobucket account and the link disappears, giving no picture from that point on. The same would be true with other photo managemt services like picassa and imageshack etc.