Garment design tool with image preview

A method comprising:

• providing a garment previewing tool that allows previewing on a computer screen of a jeans garment customized by a user with a finishing pattern created using a digital input file, wherein the garment previewing tool comprises
• showing a first garment preview image on the computer screen comprising a jeans base image for a selected garment base,
• allowing the user to select a surface pattern, wherein the surface pattern is associated with a digital input file to produce that surface pattern onto a jeans garment,
• showing a second garment preview image on the computer screen comprising the selected surface pattern in combination with the jeans base image, wherein the second garment preview image is generated by
• generating an adjusted base image from the jeans base image without the selected surface pattern,
• generating a pattern mask based on the digital input file associated with the selected surface pattern, and
• for a pixel at a pixel location of the second garment preview image, obtaining a first contribution by combining a first value associated with a pixel of the pattern mask at a pattern mask pixel location that corresponds to the pixel location of the second garment preview image and a value of a pixel of the base image at a base image pixel location that corresponds to the pixel location of the second garment preview image.