1. A computer-implemented method for restoring appearances of scans of damaged physical documents, the computer-implemented method comprising: receiving a scanned image of a physical document that includes ink writing; determining an ink bleed model by analyzing colors of pixels of the scanned image of the physical document, the ink bleed model comprising a gradient of colors from ink colors having ink bleed at different rates on the physical document; and restoring an appearance of the scanned image of the physical document by changing the colors of the pixels of the scanned image of the physical document to reduce the ink bleed based on the ink bleed model, wherein changing the colors of the pixels of the scanned image comprises: detecting a sequence of adjacent pixels corresponding to the gradient of colors of the ink bleed model, determining a scaling factor based on the sequence, predicting an original stroke based on the scaling factor, and based on the predicted original stroke, changing the colors of the pixels by mixing the pixels with an ink color.