Exactly! Each panel was first realized by Segrelles as an oil painting. These were then reduced in size, provided with text/speech-bubbles and assembled into the final pages. If you are interested in the art of Segrelles, I recommend the German collectors edition of El Mercenario, published by Splitter. It has an amazing making off section at the end of each volume, that can be easily translated by using OCR and deepl in case you don´t speak German. On top of that it features a print quality true to the actual art, which sadly can´t be said about a lot of El Mercenario editions.