As stated before, the image is treated as text, so the bottom is to accommodate for those pesky: "p,q,y,g,j"; the easiest solution is to assign the img display:block; in your css.
But this does inhibit the standard image behavior of flowing with the text. To keep that behavior and eliminate the space. I recommend wrapping the image with something like this.
<style>
.imageHolder
{
display: inline-block;
}
img.noSpace
{
display: block;
}
</style>
<div class="imageHolder"><img src="myimg.png" class="noSpace"/></div>