Edit in JSFiddle


              
<div class="wrapper"><img src="http://dummyimage.com/300x100/4B97D6/fff&text=originale"></div>
<div class="wrapper soluzione1"><img src="http://dummyimage.com/300x100/4B97D6/fff&text=line-height:0"></div>
<div class="wrapper soluzione2"><img src="http://dummyimage.com/300x100/4B97D6/fff&text=display:block"></div>
<div class="wrapper soluzione3"><img src="http://dummyimage.com/300x100/4B97D6/fff&text=vertical-align:bottom"></div>
.wrapper {width: 300px; margin: 10px; border: solid #AA0000;}
.soluzione1 {line-height: 0;}
.soluzione2 img {display: block;}
.soluzione3 img {vertical-align: bottom;}