A computer-implemented method includes receiving a digital representation of an image and generating CAD sketches from it. The number of surfaces in a CAD model depends upon the number entities at the sketch level. The method keeps the number of created sketch entities and constraints to a minimum. The method includes a scalable approach for a range of images. Each contour is represented by a sequence of points following a path corresponding to a boundary in the image. The method includes classifying each point in a particular one of the contours as a curve region or a corner region contour point, thereby segmenting the contour into plurality of curve regions separated by corner regions. The method includes optimally fitting a curve to each one of the curve regions to create the best possible representation of the curve region. Additionally, the refine algorithm automatically improves the fit wherever needed.