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).

The present invention discloses a gray scale adjustment method and device for a display panel. The method includes: performing an image acquisition on the display panel to obtain a current image; identifying a relationship between a sum of gray scale values of all pixels in the current image and a target value by a distinguishing method, in order to identify an uneven block in the current image; detecting an original output luminance and an original input gray scale of the uneven block; determining a target input gray scale corresponding to a preset target luminance according to an actual gamma curve value obtained by testing the display panel; and taking a difference between the original input gray scale and the target input gray scale as a gray scale compensation value of the uneven block.

Disclosed are a method and a device for adjusting grayscale of display panel, the method includes: obtaining a current image by performing image acquisition of a display panel; identifying an nonuniform block in the current image, detecting original output brightness and original input grayscale of the nonuniform block; determining a target input grayscale corresponding to a preset target brightness according to an actual Gamma curve value, wherein the actual Gamma curve value is obtained by testing the display panel; taking a difference between the original input grayscale and the target input grayscale as a grayscale compensation value of the nonuniform block.

Disclosed is a method for converting image data. The method includes: acquiring image data of a target image, wherein the image data includes first pixel values of m pixels in the target image, each of the first pixel values includes a first color value of at least one color channel, the first color value being within a target color value interval of the at least one color channel; dividing the target color value interval into n color value partitions; determining a color value partition where the first color value falls from the n color value partitions; and converting the first color value into a second color value according to a position of the first color value in the color value partition, the number of bits occupied by the second color value being less than the number of bits occupied by the first color value.

An object of the present disclosure is to reduce density unevenness and streaks of an image that is printed in a case where it is not possible to implement sufficient correction only by the correction for a defective nozzle. One embodiment of the present invention is an image processing apparatus that performs processing for an input image for an image forming apparatus performing printing on a printing medium by using a print head in which a plurality of printing elements is arrayed, the image processing apparatus including: a storage unit configured to store density characteristic information indicating an output density for each tone for each of the printing elements; a target value acquisition unit configured to acquire a target characteristic indicating a target value for each tone; and a first correction unit configured to correct the input image based on the density characteristic information and the target value.

A recording step for driving a recording head having a plurality of nozzles arranged in a first direction, and recording a TP in which a plurality of patches having densities different from each other are arranged in a second direction, a reading step, a calculating step for calculating a correction value for each raster line, and a setting step for setting the correction value for each raster line as a correction value to be used for recording processing are included, and among the plurality of patches constituting the TP, when a highest density patch is a first patch and patches other than the first patch are second patches, in the recording step, a length in the second direction of the first patch is made greater than a length in the second direction of at least one of the second patches and the TP is recorded.

The conversion of the dot percentages using the first conversion table Td1 and the second conversion table Td2 is performed for the gradation data Dh by the defective nozzle corrector 95. Here, the first conversion table Td1 converts the dot percentages of the pixels Px corresponding to the normal nozzles Nn having no discharge defect by the first rate Rd1 lower than 100%, and the second conversion table Td2 converts the dot percentages of the pixels Px corresponding to the surrounding nozzles Na located around the defective nozzle Nd by the second rate Rd2 higher than the first rate Rd1. Then, the shading correction is performed for the defect complemented gradation data Dc obtained by converting the dot percentages in this way by the shading corrector 96.

To enable highly accurate density unevenness correction while suppressing a reduction in productivity in printing accompanying correction value calculation for density unevenness correction. Based on an image obtained by scanning a chart including patches having uniform density for each tone value, a density characteristic of each nozzle is acquired. A non-ejectable nozzle that cannot eject ink normally is detected by analyzing a pattern for detecting the non-ejectable nozzle in the image obtained by scanning the chart. At the time of acquiring the density characteristic, the density characteristic is acquired based on a density measured value of an area of the image, which corresponds to a nozzle that is not detected as the non-ejectable nozzle.

A print position adjustment mode is performed with high accuracy while consumption of print media is saved. An inkjet printing apparatus prints an adjustment pattern including multiple patches for adjusting print positions of dots by a print head on a print medium. Patches set next to each other in a scanning direction are printed above platen ribs at intervals based on rib pitches at which the platen ribs are arranged.

On a recording sheet of a first size, an image combined with gradation patches of a plurality of colors is printed, on a recording sheet of a second size smaller than the first size, images combined with the gradation patches of the plurality of colors are divided and printed into a plurality of recording sheets, color measurement is performed on each of the gradation patches, and gradation correction data is generated.