Currently, a particular scan resolution has to be defined before a scanner starts working. Two problems arise from this process. Firstly, no matter how different two pages contents are, they will be scanned into the same resolution. For example, after scanning, a blank page and a fine-detailed drawing will have the same resolution. Secondly, for one scanned page, every part of its output would have the same resolution, whatever their contents are. These problems will cause unnecessary waste of memory used to store scanned images. So a method to decide the minimum acceptable scan resolution is needed. But current image quality estimators are not suitable for estimating image quality at different resolutions. This paper proposes four features to assess image qualities at different resolutions, namely 75, 100, 150, 200 and 300 dpi. The features are tile-SSIM mean, tile-SSIM standard deviation, horizontal transition density, and vertical transition density. Tests on images containing different contents show that these features are promising in evaluate image qualities across different scan resolutions.