I'm writing an image gallery script for my website portfolio and would like to make use of the embedded EXIF thumbnails within my images rather than having to create and manage separate thumbnail images. I can successfully extract and display the embedded EXIF thumbnails but they are much smaller than I would like them to be. I've noticed that they change sizes depending on the size of the original. For example, a 1920x1280 image will yield a 160x107 thumbnail, whereas a 5959x3973 will have a 256x171 thumbnail.
I was hoping that there is some way to explicitly define the EXIF thumbnail size and/or ratio relative to the original image so that when I export my images from Lightroom they will have larger thumbnails embedded into the EXIF metadata.