15. A non-transitory computer-readable storage medium storing executable computer program instructions for performing steps comprising: identifying text quality scores associated with a plurality of digital text characters generated from the document image, a text quality score for a target character describing a likelihood of the target character being at a location of the target character within the document image; identifying a plurality of subsets of characters having associated text quality scores that differ from text quality scores associated with neighboring characters in the document image by more than a threshold value; segmenting the document image into a plurality of segments associated with different text quality scores responsive to the identified plurality of subsets of characters; determining a representative text quality score for each segment of the document image; and storing the representative text quality scores in association with the segments.
15. A non-transitory computer-readable storage medium storing executable computer program instructions for performing steps comprising: identifying text quality scores associated with a plurality of digital text characters generated from the document image, a text quality score for a target character describing a likelihood of the target character being at a location of the target character within the document image; identifying a plurality of subsets of characters having associated text quality scores that differ from text quality scores associated with neighboring characters in the document image by more than a threshold value; segmenting the document image into a plurality of segments associated with different text quality scores responsive to the identified plurality of subsets of characters; determining a representative text quality score for each segment of the document image; and storing the representative text quality scores in association with the segments. 17. The storage medium of claim 15 , wherein identifying a subset of characters having associated text quality scores that differ from text quality scores associated with neighboring characters in the image comprises: identifying neighboring characters in the document image having similar text quality scores; and adding the neighboring characters in the document image having similar text quality scores to the subset of characters.