An algorithmic based method and apparatus for registering halftone color separations using edge based registration techniques. Digital pictures are taken at two locations on each film, and, following optimal thresholding of the data, the edges are located by application of a Laplacian of a Gaussian edge detection operator. Sampling is used to reduce the computational requirements, and full resolution is restored by interpolation. The edge locations are corrected for operator edge bias, and the corrected edge points are linked into segments which are registered by the parameter space method. The initial offset is corrected for size differences by application of least squares correction techniques.

An automatic register control system for multi-color rotary presses having adjusting means for adjusting the phase on a plate cylinder of each printing section, comprising a registering error detecting device that reads register marks each printed on a traveling paper web by each printing section with a CCD camera as image data, corrects the image data using inherent correcting means, and detects the characteristic points of the register marks as their coordinates to detect a deviation between the actual coordinates of the detected characteristic points and the desired coordinates thereof, and adjusting signal output means for outputting an adjusting signal to the adjusting means to adjust the phase of the plate cylinder in each printing section on the basis of the deviation detected by the registering error detecting device, thereby automatically adjusting registering errors in the multi-color rotary press.

In performing markings in semiconductor manufacturing devices, the positional discrepancy between printing plate and plate holder is first detected by a camera. After correcting such a discrepancy, the printing plate is positionally fixed and then printing is performed. The printing plate is rotated and moved horizontally in any directions when positional discrepancy is detected and corrected, and an image signal of such positional discrepancy supplied from the camera which is set to face the plate holder is processed to be shown on a monitor for executing correction of the discrepancy.

An algorithmically based method and apparatus for registering halftone color separations using edge based registration techniques and three registration points on each film separation in order to handle image stretching in both directions. Improved techniques include the use of gray level transformation, an improved U.S.C. predicate, double accuracy interpretation after systematic convolution sampling, finer angle sweeping to achieve smoother edge transitions around sharp corners, elimination of gaps in the edge continuity, enhancement of final edge linking, a more accurate and robust segment matching algorithm, invocation of a registration quality index for quality control checking of each segment picture registration, and reduction of machine cycle time by performing computations concurrently with machine movement.

A method of making color and gradation correction performs color and gradation correction differently for a human subject image and a computer graphic image before or after composing these images. A gradation correction is carried out by the use of linear table data written in a look-up table for computer graphic images and non-linear table data for human subject images. A color correction circuit for transforming image data by the use of a matrix calculation comprises three look-up table memories and an adder for adding together outputs from the look-up table memories for each color to be color corrected. In these three look-up table memories, different table data are written in, according to the kinds of human subject image and computer graphic image. There are provided a plurality of different table data for human subject images and computer graphic images, respectively and suitable table data are selected according to a human subject image and a computer graphic image to be composed.