Agfa-gevaert Ag

Hermann Fuchsberger

Eduard Wagensonner

Wolfgang Ruf

Klaus Birgmeir

A colored original is scanned point-by-point and density values are generated for each point in the primary colors red, green and blue. The points are divided into groups and the density values for each primary color are averaged over the respective groups. The averaged density values for each group are transformed into a set of converted values including a luminance value as well as first and second chrominance values. The range spanned by the luminance values is divided into segments and each set is assigned to a respective segment. The sets are classified as color dominant or color nondominant by comparing the saturation value of each set with a threshold value. For each, segment the first and second chrominance values of the nondominant sets are respectively added to yield first and second sums. The first and second sums are shifted relative to the gray point to generate corrected first and second sums. Each pair of uncorrected first and second sums is converted into uncorrected red, green and blue density values whereas corrected density values are obtained from the corresponding pair of corrected first and second sums. For each primary color, the corresponding uncorrected and corrected density values define a point in a coordinate system of uncorrected density versus corrected density. By plotting the points from the various segments, a correction curve can be established for each primary color.

Electronic image processing with automatic color correction

An improved method for correction of color saturation, in electronic image processing, automatically compensates for brightness changes resulting from contrast processing. The method is used with electronic image processing, in which a two-dimensional original image is electro-optically scanned along rows and columns for three primary colors, the resulting image signals are transformed into a luminance signal Y and two color-difference or chrominance signals C1, C2, and the luminance signal is modified by electronic contrast processing. The invention improves the basic image processing method by measuring the luminance signals Y.sub.1 and Y.sub.2 which occur, respectively, before and after contrast processing, and multiplying their quotient Y.sub.2 /Y.sub.1 by each of the two chrominance signals C1, C2. This compensates automatically for the increase in color saturation which accompanies a brightness reduction and for the decrease in color saturation which accompanies a brightness increase.

Method of correcting color saturation in electronic image processing

An original to be copied is electrooptically scanned point-by-point. The resulting imaging signals are stored in a first memory and then forwarded to a first image processing unit where the signals are electronically corrected to enhance the image of the original. The corrected signals are loaded into a second memory. A portion of the corrected signals is recalled from the second memory and sent to a third memory. This portion of the corrected signals is then transmitted to a second image processing unit and thereafter converted into a low-resolution video image which can be inspected to determine image quality. If image quality is satisfactory, the contents of the second memory are sent to an exposure unit which prints a high-resolution image of the original on copy material. Imaging signals for a second original are loaded into the first memory as the contents of the second memory are recalled for printing. The second processing unit functions to adjust the video image so that it closely corresponds to the printed image of the original.

Method of and apparatus for copying originals in which an image to be

The invention relates to a method and apparatus for electronic contrast valuation of two-dimensional transparent original images, in which the original images are electro-optically scanned by rows and columns. The image signals, corresponding to the image elements or pixels, and possibly needing correction, are subjected to frequency filtering, in which they are modified by a low-pass filter. The resulting low-pass signals are summed with corresponding high-pass signals obtained by subtraction of low-pass signals from the original image signals. The amplification factor for the high-pass signal is determined according to a non-linear transfer characteristic function K2, such that small signals corresponding to low image contrast are more greatly amplified (amplification S.sub.1) than are large signals corresponding to high image contrast (amplification S.sub.2), and that the low-pass signals are modified according to a non-linear gradation characteristic function K1 prior to the addition of the high-pass and low-pass signals.

Method of and apparatus for electronic contrast enhancement of

A method for adjusting the color saturation during electronic image processing, in which a two-dimensional original image is electro-optically scanned along rows and columns for three primary colors and the resulting image signals are transformed into a luminance signal Y and two color-difference or chrominance signals C1, C2. A pre-selected adjustment of color saturation is used, in which, in accordance with a non-linear characteristic curve, small chrominance signals C1, C2 are more amplified than larger chrominance signals C1, C2 corresponding to a higher degree of saturation.

Method and apparatus for adjusting color saturation in electronic image

A colored original to be reproduced is scanned point-by-point in each of the three primary colors. The resulting imaging signals are processed to generate a luminance signal and a pair of chrominance signals. The luminance signal is branched into a high-pass filter channel and a low-pass filter channel. The high-pass portion of the luminance signal is amplified in accordance with a sublinear characteristic function which causes signals of small amplitude to be amplified to a greater degree than signals of large amplitude. The low-pass portion of the luminance signal is modified per a non-linear characteristic gradation function. The thus-modified high-pass and low-pass portions of the luminance signal are added to yield an enhanced luminance signal. The enhanced luminance signal is divided by the original luminance signal and each of the chrominance signals is multiplied by the resulting quotient. This automatially compensates for the changes in color saturation which accompany changes in brightness. After the multiplication, the chrominance signals are amplified in accordance with a sublinear characteristic function which causes signals of small amplitude to be amplified to a greater degree than signals of large amplitude. This characteristic function further has a form such that no additional ampification takes place beyond a predetermined threshold limit.

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Ismaning, Germany

Hermann Fuchsberger