Image Grid Fluid Layout (Responsive)

Image Grid Fluid Layout (Responsive)

I am working on image grid(4 columns) with fluid layout. In jsfiddle
currently the height is set to auto but it's not coming the way I am
expecting because the image dimensions are different. The image size is
not proportional after fixing the height. I know, it will work properly
when image(width/height) will be equal but I don't want to do this because
images will be coming dynamically(same width/different height). Is there
any way it can be fixed for different image dimensions? Fiddle below
img{
width:100%;
//height:150px;
height:auto;
}
JSFiddle