Image processing device, image processing method, and non-transitory computer-readable medium therefor

An image processing method for printing an image, comprising;

• obtaining input image data representing an input gradation value for each of multiple pixels;
• and
• generating output image data representing a dot formation state for each of the multiple pixels by executing a halftone process with respect to the input image data,
• wherein the halftone process includes a state selecting step of selecting, from among Q+1 dot states, the dot formation state of a pixel of interest among the multiple pixels, the Q being an integer of 2 or more,
• wherein the Q+1 dot states include a non-dot state indicating no dots and Q with-dot states indicating dots of sizes different from each other,
• wherein the state selecting step includes:
• a threshold determining process of determining Q threshold values to be associated with the Q with-dot states;
• calculating a compensated gradation value of the pixel of interest using an input gradation value of the pixel of interest and a first error value indicating an error value distributed to the pixel of interest from L distribution pixels located around the pixel of interest, the L being an integer of 2 or more;
• selecting the dot formation state of the pixel of interest by comparing the compensated gradation value of the pixel of interest and at least one of the Q threshold values;
• and
• calculating a second error value indicating an error value of the pixel of interest using a reference gradation value to be associated with the dot formation state of the pixel of interest from among Q+1 reference gradation values and the compensated gradation value of the pixel of interest, the Q+1 reference gradation values to be associated with the Q+1 dot states,
• wherein, in the threshold determining process, the Q threshold values are determined using multiple parameters including the input gradation values of the pixel of interest and Q reference gradation values to be associated with the Q with-dot states.

A non-transitory computer-readable recording medium containing computer-executable instructions executable by a computer of an image processing device configured to print an image, the computer-executable instructions causing, when executed by the computer, the image processing device to perform:

• obtaining input image data representing an input gradation value for each of multiple pixels;
• and
• generating output image data representing a dot formation state for each of the multiple pixels by executing a halftone process with respect to the input image data,
• wherein the halftone process includes a state selecting process of selecting, from among Q+1 dot states, the dot formation state of a pixel of interest among the multiple pixels, the Q being an integer of 2 or more,
• wherein the Q+1 dot states include a non-dot state indicating no dots and Q with-dot states indicating dots of sizes different from each other,
• wherein the state selecting process includes:
• a threshold determining process of determining Q threshold values to be associated with the Q with-dot states;
• calculating a compensated gradation value of the pixel of interest using an input gradation value of the pixel of interest and a first error value indicating an error value distributed to the pixel of interest from L distribution pixels located around the pixel of interest, the L being an integer of 2 or more;
• selecting the dot formation state of the pixel of interest by comparing the compensated gradation value of the pixel of interest and at least one of the Q threshold values;
• and
• calculating a second error value indicating an error value of the pixel of interest using a reference gradation value to be associated with the dot formation state of the pixel of interest from among Q+1 reference gradation values and the compensated gradation value of the pixel of interest, the Q+1 reference gradation values to be associated with the Q+1 dot states,
• wherein, in the threshold determining process, the Q threshold values are determined using multiple parameters including the input gradation values of the pixel of interest and Q reference gradation values to be associated with the Q with-dot states.