Method for the removal of scratches from digital images
View Patent ↗The present invention is in the field of imaging and more specifically image analysis. An object of the invention is to provide for a method which restores a digitized image or a series of digitized images automatically, by eliminating straight or virtually straight scratches in the images. The method of the invention eliminates scratches in still or animated digital images by using the residual image information in the altered areas of the images. This method can be used in the field of the restoration of films and television documents and for retouching and restoring photographic images.
1. A method for automatically restoring in real time at least one digitized original image that has been altered by one or more straight or virtually straight scratches, by providing detection masks or coordinates of areas of the image to be restored which correspond to the scratches, the method comprising the steps of:
a) calculating and recording for each line of pixels in an area to be restored perpendicular to a theoretical axis of a scratch, an absolute value of a difference in intensity between two pixels located on said line of pixels, immediately to the left and right of the area to be restored, outside said area;
b) calculating and recording for each line of pixels in the area to be restored, a width and a height of a working area which represents an area of pixels centered around said line of pixels, said width being approximately that of the area to be restored and said height depending on the values calculated in said step a);
c) calculating and recording for each column of pixels in the working area defined in said step b) parallel to a theoretical axis of the scratch, an average value of respective intensity of the pixels forming said column of pixels in the altered image;
d) calculating and recording, by linear interpolation perpendicular to the theoretical axis of the scratch between the pixels located immediately to the left and right of the area to be restored defined in said step a), a local value of an intensity of an estimated profile and characteristic of the scratch, for each pixel in the line of pixels in the working area; and
e) calculating and recording a local corrected intensity value for each pixel in the line of pixels in the working area, by subtracting the local value obtained in said step d) from the value of the intensity of said pixel in the altered image, so as to automatically restore the original image.
2. The method of claim 1 , wherein a virtually straight scratch is one where a maximum positional deviation of at least one of the pixels on the line that represents a real axis of said scratch in relation to its theoretical axis, is equal to or less than 3 pixels.
3. The method of claim 1 , wherein the height calculated for the working area is directly proportional to the absolute value of the difference in intensity calculated in said step a).
4. The method of claim 1 , wherein the working area comprises lines for which an absolute value of the difference in intensity calculated in said step a) is less than a given intensity threshold, which depends on a homogeneity of a texture of the original image.
5. The method of claim 1 , wherein the height of the working area is preferably included between 5 and 100 lines of pixels of the original image.
6. The method of claim 1 , wherein a width of the straight or virtually straight scratch is equal to or less than 15 pixels.