A method and apparatus for reproducing an original image, having a scanner which scans and digitizes the original image into pixels, a controller coupled to the scanner to receive the digitized original image, and which produces a first signal corresponding to a gray level halftoned representation of the digitized original image, and a printer coupled to the controller to receive the first signal and which produces a gray level halftoned reproduction of the original image. The controller groups the pixels into cells that each have a determined cell gray level, and controls the formation of dots within the pixels of an individual cell by the printer such that for each increase in cell gray level, a dot at at least one of the pixels in the cell forms to a larger dot-size. Sequential forming of the dots occurs at the pixels in the cell in a pre-defined order such that each dot is formed to a first dot-size less than a maximum dot-size before beginning the formation of a dot at another pixel within the cell. When all of the dots in the cell have been formed to the first dot-size corresponding to a specific cell gray level, the dot-size of each of the dots is increased in the pre-defined order to a second dot-size, corresponding to increasing cell gray levels.
A proofing method enabling accurate visual simulation of high resolution screens, including all screening effects such as moire, uses a low resolution continuous tone proofer. The resolution and addressability of the proofer has to be better than the dot resolution of the screen, but can be much lower than the pixel resolution (a dot consists of at least 10.times.10 pixels). For example, a screen made of 3.times.3 pixels dots can simulate a screen made of 12.times.12 pixel binary dots if the grey scale of each one of the 3.times.3 dots is adjusted to kept the visual centroid of the 3.times.3 dot at the same position and intensity as the 12.times.12 pixel dot. The low spatial resolution of the unaided eye cannot see the difference between the two screens.
A halftone screen is presented for use in combination with reproduction devices that are capable of rendering more than two tone levels. The screen is optimized to minimize both tone and color shift in the presence of variations in the printing process. The intermediate density levels, which are assigned to a minority of the microdots within each halftone cell, are different within adjacent halftone cells. FIG. 9
Pixels are grouped into groups of pixels, comprising a plurality of pixels each, and representative tone values are determined for each of a plurality of regions into which the groups of pixels are split. Decisions are made as to whether or not to output dots to the individual pixels in the group of pixels based on the multilevel halftoning resultant values obtained through performing multilevel halftoning on the representative tone values, to thereby output an image. The multilevel halftoning resultant values can accelerate the creation and transfer of data, enabling rapid outputting of images. Moreover, based on tone values of the individual pixels within a group of pixels, a decision is made as to whether or not to split the group of pixels, where, for groups of pixels for which the decision is to not split the group of pixels, the representative tone value obtained for the group of pixels may be subjected to multilevel halftoning to determine whether or not to form dots, based on the multilevel halftoning resultant values. The present composition enables the high speed outputting of high quality images using simple processes.
A data processing part in a printer controller performs multivalued dither processing whereby image data is processed for images of characters and thin lines with a high definition, and for pictures with a high color gradation, and the image quality deterioration at the boundary region between an edge region and a non-edge region can be avoided. The data processing part performs discrimination of an edge region, a non-edge region, and a boundary region between the edge and non-edge regions. Furthermore, the data processing part performs multivalued dither processing by using a prepared dot distribution type dither matrix for the edge region, a prepared dot concentration type dither matrix for the non-edge region and a prepared dot distribution and concentration mixing type dither matrix for the boundary region. Furthermore, the amount of image data to be processed is reduced by dividing an image frame into a plurality of pixel blocks and expressing an image of each pixel block with a few of approximate color data and approximate color arrangement data.
Method to improve the printing quality at reproduction of half-tone originals by means of printers of the type, in which a number of dots are brought together in a cell (pixel). A minimum of two dots form a cell where each dot in the cell is controlled individually with respect to the size and/or the color value. The dots form a pattern in each cell, which is variable with respect to the number of dots, the dot size and/or the dot color value.
