Ricci Vectorized Map

This gist shows the vectorized version of the first three panels of the "Kunyu Wanguo Quantu".

Use imagemagick for converting the jpg file into a bitmap.

convert ../Kunyu_Wanguo_Quantu_by_Matteo_Ricci_Plate_1-3.jpg ../Kunyu_Wanguo_Quantu_by_Matteo_Ricci_Plate_1-3.bmp

The potrace tool is then used to vectorize the bitmap.

./potrace -k 0.2 --svg ../Kunyu_Wanguo_Quantu_by_Matteo_Ricci_Plate_1-3.bmp -o ../Kunyu_Wanguo_Quantu_by_Matteo_Ricci_Plate_1-3.svg

Look at

-t n, --turdsize n suppress speckles of up to this many pixels.

-k n, --blacklevel n set the threshold level for converting input images to bitmaps. The potrace algorithm expects a bitmap, thus all pixels of the input images are converted to black or white before processing begins. Pixels whose brightness is less than n are converted to black, all other pixels to white. Here n is a number between 0 and 1. One case is treated specially: if the input is in an indexed color format with exactly 2 colors, then the blacklevel is ignored and the darker of the two colors is mapped to black.