This is called Sekka shibori which is one of Itajime Shibori dye techniques. It's created by pleating, folding, clamping and dyeing the fabric. The fabric has to be folded and pressed neatly to create nice and precise patterns.
TRY- Shibori "Linen Baby Wrap Sekka Shibori Dye: Part 2 This is the second half of my Sekka Shibori experiment. The first half, which covers the basics and folding can be read here. This is where we left off: a stack of folded linen.