1. An image processing device comprising: an original image data acquirer configured to acquire original image datasets for a plurality of colors each having a first resolution, the plurality of colors including a first-resolution print color to be printed at the first resolution and a second-resolution print color to be printed at a second resolution lower than the first resolution and different from the first-resolution print color, the original image datasets including a first original image dataset for the first-resolution print color and a second original image dataset for the second-resolution print color; an edge detector configured to detect a longitudinal edge and a lateral edge of each of a first image in the first original image dataset and a second image in the second original image dataset; a resolution converter configured to convert the first resolution of the second original image dataset into the second resolution by performing a density averaging on each group of a plurality of pixels of the second original image dataset having the first resolution, to obtain a resolution-converted image dataset; a density corrector configured to perform a density correction processing on the resolution-converted image dataset to obtain a density-corrected image dataset by determining whether pixels in the resolution-converted image dataset include first pixels each being a pixel located at a position including the longitudinal edge in the second image, determining whether the pixels in the resolution-converted image dataset include second pixels each being a pixel located at a position including the lateral edge in the second image, upon determining that the pixels include the first pixels, determining whether each of the first pixels is a first deletion-target pixel, patterns of the longitudinal edges in regions in the first and second images corresponding to the first deletion-target pixel being the same, upon determining that the pixels include the second pixels, determining whether each of the second pixels is a second deletion-target pixel, patterns of the longitudinal edges in regions in the first and second images corresponding to the second deletion-target pixel being the same, correcting a density of the first and second deletion-target pixels to “0”, and correcting a density of respective pixels other than the first and second deletion-target pixels among the first and second pixels to a value equal to or larger than an original density of the respective pixels; and a print image data generator configured to generate print image datasets for the respective plurality of colors based on the first original dataset and the density-corrected image dataset, the print image datasets being in a format supported by a printing machine capable of printing the first-resolution print color at the first resolution and the second-resolution print color at the second resolution.