Image inside div has extra space below the image
By default, an image is rendered inline, like a letter so it sits on the same line that a, b, c and d sit on.
There is space below that line for the descenders you find on letters like g, j, p and q.
Demonstration of descenders
You can:
adjust the vertical-align of the image to position it elsewhere (e.g. the middle) or
change the display so it isn't inline.