Abstract: An image output system processes an input image signal from an image signal source, such as a television camera, to produce an output image signal to record an image on an image recording medium. The input image signal is logarithmically converted into an image signal which matches the image output system, using a first look-up table which is selected to match the image signal source. Then, the image signal, which has been converted by the first look-up table, is linearly converted into an image signal based on first corrective parameters set to achieve given color qualities. The image signal, which has been linearly converted, is converted an image signal which matches the image recording medium, using a second look-up table which is selected to match the image recording medium. The image signal, which has been converted by the second look-up table, is exponentially converted into an exponential output image signal based on second corrective parameters set to achieve given color qualities.

Abstract: An image processing method for producing color-corrected output color signals in response to respective hue-separated input color signals, such as from the output of a scanner, having a reduced memory requirement for transformation coefficients yet with little sacrifice in transformation accuracy. In a preferred embodiment, transformation coefficients for each of three output color signals are produced having individual bit lengths determined in accordance with a degree of correlation with the respective input color signal. The input color signals are subjected to transformation operations using the stored coefficients.

Abstract: Tone correction for input video signals is performed on the basis of look-up table data. The state of color tone is decided by using chroma signals each corresponding to one of input video signals, and a luminance signal produced from the input video signals. In response to the particular state decided, signals are produced by applying color correction level adjustment to the input video signals. A highlight point and a shadow point are set up based on one of such adjusted signals so as to produce look-up table data for each of the input video signals. This allows input video data to be subjected to tone correction which corresponds to particular photographing conditions, thereby eliminating overcorrection or undercorrection. Hence, the operator's decision as to the state of color tone is needless so that the ease of operation is promoted.

Abstract: The gradation correction of input video signals is conducted in the gradation correctors based on lookup table data. The cumulative histograms of the input video signals are generated in cumulative histogram generators to set highlight points and shadow points. Based on the highlight and shadow points, the standard lookup table data stored in the standard lookup table storage is converted in lookup table data associated with the input video signals and outputted to gradation correctors. According to this method, an appropriate gradation correction can be achieved depending on the input video signals. The standard lookup table storage need only be loaded with the standard lookup table data, namely, a great volume of lookup table data need not be stored.