Photo restoration

Digital photograph restoration is the practice of restoring the appearance of a digital copy of a physical photograph which has been damaged by natural, man made, or environmental causes or simply affected by age or neglect.

Digital photograph restoration uses a variety of image editing techniques to remove visible damage and aging effects from digital copies of physical photographs. Raster graphics editors (see list below) are typically used to repair the appearance of the digital images and add to the digital copy of the photo where pieces of the physical photograph are torn or missing. Evidence of dirt, scratches, and other signs of photographic age are removed from the digital image manually, by painting over them meticulously. Unwanted color casts are removed and the image's contrast or sharpening may be altered in an attempt to restore some of the contrast range or detail that is believed to be in the original physical image. In addition image processing techniques such as image enhancement and image restoration are also applicable for the purpose of digital photograph restoration.

...
Wikipedia