Many years ago when I still was a young navigations officer on a Norwegian laker,we were taken to som delightful areas around Nassau
by the ship's agent.
I remember jumping out in the shallow water
to pull the boat up on the beach,landing on a nasty sea urchin which was rather painful.
Hobbling around on one foot,our host said 'let me see the sole of your foot'
As I raised it,he grabbed a hefty piece of wood and gave the painful area of black spine spots a good hard wallop. I said 'hey,what are you doing,that was very painful! He laughed and said that was the only way to pulverize/disintegrate the brittle embedded needles of the sea urchin. He was right,not long after I walked without pain. memories .. memories...
Well, the charts are a combination of graphic preparation work to straighten and clean up the original bitmap. When you are happy about its appearance,you can for example also add a pale blue/grey color to the sea areas so you later will be able to dim the chart for night sailing. Microsoft does not allow dimming of white colors.
Then I would suggest .jpg as the initial format of the bitmap. Reduce the resolution to 75 dpi which is the maximum a PC screen
can display anyway and will reduce the size of the map. Then use a .jpg compressing software
to reduce the file size further before using the FREE Gimp2 software
to reduce the colors to 127 and finally store it as a .png file in the 'Chartconvert' directory.
Now use FREE 'ChartcalII' to load up the .png chart and enter all the geo locs you can find,generally in a box shape.. enter also all the chart details such as scale,soundings etc. not forgetting to enter (for example) 'GE9999' in the # box at the top right. Then enter the geo locs of all the map corners before saving the CHARTCAL.DIR header file to the 'Chartconvert' directory.
Now start Chartconvert and load up the previously stored .png file and the program will start the conversion process to a .kap file.
A bit of a proceedure but easy when you have converted a few charts.
I attach a screenshot of MY 'Chartconvert' directory so you can see which programs you will need for the conversion process.
Good luck! and Fair Winds!!