1. A method, comprising: obtaining an image; identifying a candidate location in the image that likely contains a text character; determining candidate features for the candidate location; downscaling the image into a first downscaled image having a first resolution and a first aspect ratio; downscaling the image into a second downscaled image having a second resolution and a second aspect ratio, wherein the first resolution is different from the second resolution, and the first aspect ratio is different than the second aspect ratio; generating first contextual image gradient features for the first downscaled image comprising first magnitude values and first angles; generating second contextual image gradient features for the second downscaled image comprising second magnitude values and second angles; normalizing the first magnitude values features to a uniform scale, producing normalized first contextual image gradient features; normalizing the second magnitude values to the uniform scale, producing normalized second contextual image gradient features; combining the normalized first contextual image gradient features, the normalized second contextual image gradient features, and the candidate features; and determining that the candidate location contains at least one text character, using the combined features and at least one classifier model, wherein the first and second magnitude values are approximated, and the first and second angles are quantized.