Calibre adds margins

[GianluC03]

Ok basically I used Kindle Comic Converter to modify a Manga I purchased on kobo store, so after modifying two images I by converted the images of the original file to epub, then I got the epub on Calibre and used it to convert the file to kepub and send it to my kobo Clara hd. Long story short, the final result is terrible, because it has moderately big white margins over and under the images, which were not present on the original ebook. So I tried to just convert the images to epub with KCC and send the file to the kobo without using calibre, and the white margins weren't there, just like in the original manga. So I guess this is a calibre problem, anyone can help me? I'm using calibre mainly because I want to convert the file to kepub so it's smoother, I can zoom ecc. on my device and I use a plugin, kobo books to download the Metadata from kobo store since I'm just modifying modifying books that I've purchased there.