Summary

Updated the Bitmap header from BITMAPCOREHEADER to BITMAPINFOHEADER according to https://en.wikipedia.org/wiki/BMP_file_format#DIB_header_(bitmap_information_header)

Slightly newer version, now with bitmap size in header.

What existing problem does the pull request solve?**

Updating the header was necessary as inserting the previous version of the BMP wasn't possible into a PDF document.