Corrupt raw node stream with custom sizes

If I launch the raw node with anything other than the default width and height, when I try and view the stream in image_view, I get the error:

```
[ERROR] [1458437288.519759119]: Unable to convert 'bgra8' image for display: 'Image is wrongly formed: height * step != size  or  240 * 1360 != 337920'
```

For that example, I launched the node with size 320x240.
