A method for forming an image comprises the steps of dividing an inputted image into a plurality of unit areas, preparing at least five gradation conversion tables relating a density value of the density data to a dot generation energy value corresponding to a size of a dot to be printed, preparing a matrix dividing each of the unit areas into predetermined number of element areas, dividing each of the unit areas into predetermined number of the element areas by means of the matrix, assigning one of the plurality of gradation conversion tables to each of the element area in each of the unit area, and recording the dots converted from the density data, wherein the plurality of conversion tables are prepared in such a manner that there exists at least three converted energy values other than the minimum and the maximum values thereof at an arbitrary density value in halftone density, and wherein the plurality of conversion tables are prepared in such a manner that the number of element areas in which the minimum value of the converted energy is assigned is more than half of the number of all the element areas at the minimum density level having the maximum value of the converted energy.

An ink jet printing method comprising forming an ink image directly on a printing medium according to image data signals and fixing the image to obtain printed matter, in which tone reproduction is based on conversion of density levels of the image data into sizes of ink dots, wherein a tone conversion table is prepared based on at least five characteristic curves representing the relationship of tone values versus energy for forming the ink dots, at least three characteristics curves are prepared each at a prescribed tone value in the half tone range, each having a converted energy value other than the maximum and minimum converted energy values, and the number of dots the converted energy for which is substantially the minimum is a half or more than a half of the total number of the dots at a tone value that is the least of tone values having a dot the converted energy for which is substantially the maximum.

A drive apparatus for a self light-emitting display unit accomplishes pseudo intermediate tone display and pseudo outline compensation while maintaining a high image quality. In executing dithering-based pseudo intermediate tone display and pseudo outline compensation data conversion on pixel data corresponding to the individual pixels of the self light-emitting display unit, dither coefficients to be added to the individual pieces of pixel data are changed field by field in this dithering process. Furthermore, the pseudo outline compensation data conversion performed is associated with each dither coefficient added in the dithering process.

A printing device (10) is commanded to print a reference set of intensity values from almost white or highlight regions through almost dark or shadow regions. A measuring device (12) measures the actual outputted printer intensity levels from the printing device (10). An interpolator (14) interpolates the printer intensity levels into a best fit smooth curve plotted against the reference set of intensity levels which produces a non-linear function. A mapping means and converter (24a, 24b) calculate a set of fractional intensity values and densities which produce a linear function when mapped with the printer intensity levels. A dot area parameter calculator (28) calculates a set of dot parameters defining a configuration of a halftone dot required to fill an area within the halftone cell corresponding to each intensity level. For each position of each halftone cell, a measurement processor (30) determines a distance between a current scan position (a,b) and a nearest edge defined by the dot parameters. A gray value calculator (50) calculates a gray value for the current scan position based on the distance and angle to the nearest edge of the dot. The halftone dot is completed when a gray value is calculated for each position within the halftone cell. The gray values are stored in a look-up table (26). When a new image is to be printed, the intensity values are input (54) and the scan position is indexed (52) through all available scan positions to generate corresponding addresses in the look-up table (26), causing the corresponding gray values to be output serially in order for use by a laser diode controller (56) of a laser printer or analogous controllers in other types of printers.

The present invention is directed to a density processing method in which input gray level-output gray level data are previously generated and stored a first storing device, the input gray level-output gray level data are transferred to a second storing device, and an address in the second storing device is designated on the basis of input gray level data inputted so that output gray level data stored in the specified address in the second storing device is outputted. In the present invention, access addresses to the second storing device are converted depending on the designated copy density, so that input gray level-output gray level characteristics are converted into characteristics corresponding to the designated copy density.