A length of fabric fresh off the loom is not the same fabric that ends up in a finished trouser. What comes off the loom is called greige cloth — unwashed, unfinished, still holding the tension it picked up during weaving. Everything between the loom and the cutting table is about turning that raw cloth into something that behaves the way a trouser should.
The first step is washing. This relaxes the weave, shrinks the cloth to something close to its stable, finished dimensions, and removes any residue left over from the yarn-preparation process. Skipping this step is how you end up with a trouser that shrinks unpredictably after its first proper wash at home — we'd rather that shrinkage happen here, under control, before the cloth is ever cut.
After washing comes finishing, which is really a set of small decisions about hand-feel. Some cloths are calendared — pressed under heat and pressure to smooth the surface and add a slight sheen. Others are left with more texture, depending on what we're going for. This is also where a cloth's weight is confirmed for the final time; weaving density and finishing together determine whether a fabric drapes softly or holds a sharper line.
Every roll of finished cloth gets inspected before it's approved to move to the cutting stage. We're checking for consistency across the width of the roll, for any flaws that slipped through, and for a final match against the original colour swatch from the dyeing stage.
This is the least visible part of the whole process, and also one of the most important. A trouser can only be as good as the cloth it's cut from, and the cloth can only be as good as the care taken at this stage, well before anyone sees a finished garment.