Rollpie Fabric Texture is a free cloth generator that runs in your browser with no install. Every pixel is computed from where warp and weft cross, so the weave never blurs at any export size.
The samples panel holds six cloths, from cotton to denim. Each sample is actually woven rather than drawn, so you can see the weave and the fineness before you tap. A tap swaps the weave, density, thread width, slub, and all three colors at once, while the angle, seed, and shading stay as they were.
In the design panel you pick a part and its values appear beside it. Under Weave you set the weave type, thread density, angle, and seed; drawing a new seed replaces every slub at once. Under Thread you set the width, slub, fuzz, and shading, and warp and weft each carry their own color, thickness, and slub within it. On denim the warp is indigo and the weft is white.
In the export panel you give a width and a height and save a PNG. The view on screen is not scaled up: the image is drawn again at the size you asked for, so even large exports stay sharp. It is ready to use as a background tile or as a texture on a 3D model.