1. An image processing apparatus comprising: an image processing section which executes, when an image data to be used for a preview display to be executed before an output process for outputting an image is inputted, a plurality of types of image processing for a display process on the image data; and a segmentation process section which performs a segmentation process on the image data that is to be inputted to the image processing section; one of the plurality of types of image processing being a downsampling process; and at least one of the plurality of types of image processing other than the downsampling process being a predetermined image processing, when a degree of downsampling in the downsampling process is not higher than predetermined reference level, the image processing section executing the predetermined image processing in such a way that the predetermined image processing is varied in content according to a result of the segmentation process, and when the degree of downsampling in the downsampling process is higher than the predetermined reference level, the image processing section executing the predetermined image processing regardless of the segmentation process; wherein the image processing section includes an adjustment process section which adjusts a size of an image of the image data by performing the downsampling process in accordance with a display zoom ratio indicative of a proportion of the size of the image of the image data after the downsampling process to the size of the image of the image data before the downsampling process; when the display zoom ratio is not less than a threshold value, the image processing section executes the predetermined image processing in such a way that the predetermined image processing is varied in content according to a result of the segmentation process, considering that the degree of downsampling in the downsampling process is not higher than the predetermined reference level; and when the display zoom ratio is less than the threshold value, the image processing section executes the predetermined image processing regardless of the segmentation process, considering that the degree of downsampling in the downsampling process is higher than the predetermined reference level.