1. A method comprising: obtaining an image comprising license plate information; dividing the image into a plurality of sub-blocks; computing a spatial activity measure for each sub-block of the plurality of sub-blocks, wherein the spatial activity measure includes a two-dimensional discrete cosine transform (DCT); generating a one-dimensional activity profile for the image based on the spatial activity measure for each sub-block; determining an activity threshold based on a predetermined percentage; determining that a sub-block of the plurality of sub-blocks is an active sub-block by comparing the spatial activity measure for the sub-block with the activity threshold; generating, using one or more processors, a second image of the license plate information, wherein the second image comprises the active sub-block; and obtaining the license plate information based on the second image.