White-balance is improved when printing on colored media, while minimizing the time and use of costly materials required by present approaches. In an embodiment, the typical solid white fill or background layer is altered by including in the white layer one or more of the other colors already available in the printer to shade this layer. Thus, a small amount of cyan, for example, helps balance a pink-ish (red) media; yellow is used for blue media; and magenta is used for green media; as well as combinations thereof. A combination of transparent process inks and opaque white helps to maintain brightness (luminosity).

Luminance data indicating luminance of the print product illuminated by the lighting is calculated and processing for causing a high luminance region to have gradation characteristics is performed.

An image forming apparatus includes: an image forming unit configured to form a reference image, and a plurality of test images; a conveying unit configured to convey the sheet; a reading unit configured to read the sheet, and output read data, the reading unit including a plurality of light-receiving elements disposed along a direction orthogonal to a conveyance direction of the sheet; and a controller configured to: determine a direction in which the plurality of test images are disposed based on read data related to the reference image; determine test image read data related to test image regions corresponding to each of the plurality of test images from the read data based on the direction; and control a density of an image to be formed by the image forming unit based on the test image read data.

A printing apparatus includes a first memory, a second memory, an input circuit that alternately inputting second reference data and third reference data different from each other to the second memory, a processing circuit that performs first color processing with reference to first reference data in the first memory on print data, second color processing with reference to the second reference data in the second memory on the print data, and third color processing with reference to the third reference data in the second memory to the print data, and a printing mechanism that performs printing.

A method of determining multi-level printing parameters for a printing device includes identifying printing parameters for each of multiple colorant levels; providing at least one density measurement at a known coverage for each colorant level; providing an aim curve relating input tone value to printed density value; and identifying multiple test parameter sets. The method further includes, for each of the test parameter sets at each of multiple input tone values, determining a printed density value based on the parameters of the test parameter set and the density measurements, and determining an error value from differences between the determined printed density values and the aim curve. The method also includes selecting one of the test parameter sets using the determined error values; and communicating the selected one of the plurality of test parameter sets for receipt by the printing device for printing documents. Systems and software can employ the method.

A method of screening a continuous-tone image is configured to produce an output image to be printed on a surface. The continuous-tone image comprises a plurality of pixels having respective corresponding intended print locations. The method includes selecting a first sequence comprising a subset of the plurality of intended print locations, the first sequence being selected based on properties of the plurality of intended print locations.

For each intended print location in the first sequence, the method also includes identifying the corresponding pixel in the continuous-tone image to obtain a second sequence for an error diffusion process comprising the identified corresponding pixels in the continuous-tone image.

In a printing apparatus configured to print an image by bidirectional multipass printing while using multiple print element rows that apply color material of the same color, a high-quality image suppressed in hue unevenness and density unevenness is printed. To this end, the printing apparatus forms first and second dot patterns on a print medium in an overlapping manner. In the first dot pattern, dot arrays in which first dot groups are arranged at an interval B1 are arranged in a nozzle arrangement direction while being shifted from each other by C1 in a scanning direction of a print head. In the second dot pattern, dot arrays in which the first dot groups are arranged at the interval B1 are arranged in a nozzle arrangement direction while being shifted from each other by C2 in the scanning direction of the print head. Here, values of C1 and C2 are different.

The image forming apparatus including: a controller controlling the image forming unit to form a test image, controlling the measurement unit to measure the test image on the image bearing member, and controlling the transfer unit to transfer the test image to the sheet; a reception unit receiving a user instruction; a second generation unit generating the conversion condition based on the user instruction and the measurement result of the test image, wherein the sample image includes a first sample image, a second sample image, and a third sample image, a color difference between the first and second sample images is smaller than a threshold value, a color difference between the second and third sample images is larger than the threshold value, density of the first sample image is higher than density of the second sample image and density of the third sample image.

A method for the automated generation of reference color values for color control purposes in a printing machine by using a computer includes, within a process of setting up the printing machine for a print job, initially carrying out printing operations and using a spectrophotometer to determine coloration values for every process color used in the print job. For every process color that is used in the print job, the computer automatically selects that coloration value of a process color that has the smallest deviation from a color set point that has been established at the beginning of the job and saves this coloration value as a new reference value for this process color.

A special-purpose image processor can convert an electronic file into a bitmap by generating printing halftone dots within the bitmap based on locations of colors within the electronic file, and generating non-printing dots within the bitmap. A printing apparatus can print the bitmap, by not print marking materials where the non-printing dots are positioned within the bitmap. The special-purpose image processor can generate the non-printing dots within the bitmap by increasing the size of the printing halftone dots until they contact one another, or generating printing lines that connect the printing halftone dots to each other within the bitmap. Also, the special-purpose image processor can generate, as each printing halftone dot, a higher frequency pattern of printing dots, where the non-printing dots are generated to have a lower frequency pattern relative to that higher frequency.