Extracted images are resized to the system resolution (on Windows this is 96 dpi, on Macintosh this is 72 dpi). The extracted image contains all of the image data, but if these images are placed/opened in a page layout or an external image editing application the size will appear larger than it was in the PDF by the ratio of the original resolution divided by the system resolution. Simply resize the image dimensions and the resolution will increase or decrease accordingly.