image size should be same.. possible?

I am posting this question after going through all possible posts previously asked by others, yet couldn’t find a sure solution.

my site listing is in attached file, which shows different sizes of listing logo, irrespective of the fact that I have set the thumbnail size in settings > Media..

how can I get something like this, which is also in attachment, which shows all the image sizes are same..

see, it’s very usual case that image sizes should be different, considering the fact that all brands have their logo in different proportion.

hence, how can it make it a similar size using white background for rest unused space..rather making the image size different?

something like this mentioned in attachment..