Image Forming Device

An image forming method comprising:

• acquiring image data representing an image for one page, the image having a page length in a first direction, the image including a plurality of lines arranged in the first direction, each line including a plurality of pixels arranged in a second direction orthogonal to the first direction, the image data including a plurality of sets of line data, each set of line data indicating one of the plurality of lines and including a plurality of sets of pixel data, each set of pixel data indicating one of the plurality of pixels;
• setting at least two sets of consecutive line data among the plurality of sets of line data as determined line data, the determined line data corresponding to an area having at least two consecutive lines, the area having a prescribed length in the first direction, the prescribed length being smaller than the page length;
• determining whether a ratio of pixels to be printed to total pixels in the area is higher than or equal to a prescribed ratio based on the determined line data;
• controlling a bias applying unit to apply the first voltage between a developing roller and a supply roller when the ratio is lower than the prescribed ratio, and to apply a second voltage between the developing roller and the supply roller when the ratio is higher than or equal to the prescribed ratio, the developing roller carrying a developer, the supply roller supplying the developer to the developing roller;
• updating the determined line data by one line;
• and
• determining whether the ratio is higher than or equal to the prescribed ratio based on the updated determined line data.

A non-transitory computer-readable recording medium that stores an image forming program, the image forming program comprising instructions for:

• acquiring image data representing an image for one page, the image having a page length in a first direction, the image including a plurality of lines arranged in the first direction, each line including a plurality of pixels arranged in a second direction orthogonal to the first direction, the image data including a plurality of sets of line data, each set of line data indicating one of the plurality of lines and including a plurality of sets of pixel data, each set of pixel data indicating one of the plurality of pixels;
• setting at least two sets of consecutive line data among the plurality sets of line data as determined line data, the determined line data corresponding to an area having at least two consecutive lines, the area having a prescribed length in the first direction, the prescribed length being smaller than the page length;
• determining whether a ratio of pixels to be printed to total pixels in the area is higher than or equal to a prescribed ratio based on the determined line data;
• controlling a bias applying unit to apply the first voltage between a developing roller and a supply roller when the ratio is lower than the prescribed ratio, and to apply a second voltage between the developing roller and the supply roller when the ratio is higher than or equal to the prescribed ratio, the developing roller carrying a developer, the supply roller supplying the developer to the developing roller;
• updating the determined line data by one line;
• and
• determining whether the ratio is higher than or equal to the prescribed ratio based on the updated determined line data.