1. An image data processing apparatus comprising: a memory; a mode information receiving device configured to receive information specifying a second recording mode that is different from a first recording mode; and a controller configured to execute processes comprising: setting an image recording mode for recording an image on a recording medium to the second recording mode when the mode information receiving device receives the information specifying the second recording mode, wherein the image is to be recorded on the recording medium with a second set of image density values when the image recording mode is set to the second recording mode, wherein the image is to be recorded on the recording medium with a first set of image density values when the image recording mode is set to the first recording mode, and wherein each image density value of the second set of image density values is less than a corresponding image density value of the first set of image density values; storing image data corresponding to the image in the memory, the image data comprising a first density value for each pixel of a plurality of pixels arrayed in a matrix, wherein the first density value corresponds to the first recording mode; converting the first density value for each pixel comprised in the image data to a second density value that is less than the first density value when the second recording mode is set as the image recording mode; setting an image boundary determination threshold to one of a first threshold value and at least one second threshold value, wherein the image boundary determination threshold is set to the first threshold value when the first recording mode is set as the image recording mode, wherein the image boundary determination threshold is set to the at least one second threshold value when the second recording mode is set as the image recording mode, and wherein the at least one second threshold value is less than the first threshold value; calculating a density gradient value for each pixel comprised in the image data based on one of the first density value for the each pixel and the second density value for the each pixel, wherein the density gradient value is calculated based on the first density value for the each pixel when the first recording mode is set as the image recording mode, wherein the density gradient value is calculated based on the second density value for the each pixel when the second recording mode is set as the image recording mode; determining whether each pixel comprised in the image data corresponds to a boundary of the image based on the density gradient value for the each pixel and the image boundary determination threshold; and generating driving data for an image recording apparatus such that an amount of recording material to be recorded on a region of the recording medium corresponding to the each pixel when the each pixel corresponds to a boundary of the image is less than an amount of recording material to be recorded on the region of the recording medium corresponding to the each pixel when the each pixel does not correspond to a boundary of the image, wherein the driving data is based on the first density value for the each pixel comprised in the image data when the first recording mode is set as the image recording mode, and wherein the driving data is based on the second density value for the each pixel comprised in the image data when the second recording mode is set as the image recording mode.