Method and apparatus for partial electronic retouching of colors

The method for the partial electronic retouching of colors in color images, in which color signals obtained by point-by-point and trichromatic scanning of color originals are digitized and the digital color values of the individual color components are stored in a storage medium, and in which the stored color values are corrected by color correction values, so as to obtain retouched colors comprising the steps of:

• (a) defining color increments values (.DELTA.Y, .DELTA.M, .DELTA.C, .DELTA.K) for said individual color components, said color increment values respectively representing the smallest amount of correction for said color values (Y, M, C, K) per retouching step;
• (b) selecting a positive or negative direction of retouching;
• (c) identifying the pairs of locus-coordinates of the image points to be retouched in the color image by marking the locationally allocated points in a coordinate identification device (digitizer) with a marking means of said device, such as a coordinate pen cursor;
• (d) during coordinate identification simultaneously determining the desired retouch strength for each image point to be retouched by generating a retouch factor (r) for each identified pair of locus-coordinates with said marking means, guiding said marking means similar to a retouch brush over that area of the coordinate identification device which corresponds to the area of the color image to be retouched, said retouch factor (r) representing a plurality of color increment values which are to be summed or to be subtracted at each image point which is to be retouched;
• (e) generating correction values (Y.sub.R, M.sub.R, G.sub.R, K.sub.R) for each image point which is to be retouched by multiplying the retouch factor (r) with the individual color increment values;
• and
• (f) correcting said color values (Y, M, C, K) of the image points which are to be retouched by adding for positive retouching and subtracting for negative retouching said corresponding correction values (Y.sub.R, M.sub.R, C.sub.R, K.sub.R) of said image points in order to obtain corrected color values (Y', M', C', K') representing the retouched colors in said color image.