OK I can see from the 16, 16 at the start that the output is compatible with the Sprites library. However as the actual data below each 16x16 images is only 64 bytes, there is no mask information embedded in the array.
I do not believe any of the online tools generate image data for the
Sprites::drawPlusMask() method. When I have used this function, I have created the data by hand - mixing the image and mask data one byte after another.
Can you change you code to use
Sprites::drawSelfMasked() instead of
Ypu can read about sprites and masks in the Arduboy Magazine, Volume 7, page 33. https://issuu.com/arduboymag/docs/vol_7