Once again, messing about with ideas to make small PDFs from BHL content, using jbig2 for compression, aiming at PDFs from images 685 pixels wide (Google Books dimensions).
On a Mac OCR is almost redundant as the OS automatically OCRs images.
Turns out there is a simple way to remove (most) of the sepia tone in a BHL scan:
convert 16281585.jpg -negate -channel all -normalize -negate -channel all 16281585-rgb.jpg
where 16281585.jpg is a BHL page image. This is based on the thread Removing orange tint-mask from color-negatives.
- Page, R. (2024). Notes on transforming BHL images doi:10.59350/2gpbb-98a53