This paper reports proof of concept of a design for recognizing postal address blocks. The system must function with varying and unspecified fonts, dot matrix printing, and poor print quality. Our design achieves tolerance to differing contrast and degraded print via grayscale analysis, and omnifont capability by encoding character shapes as graphs. The current prototype, restricted to digits, successfully recognizes degraded numeric fields. There are four major modules. First, the strokes comprising each character are detected as ridges in grayscale space. Our design is tolerant of wide contrast variation even within a single character, and produces connected strokes from dot matrix print. Second, strokes are grouped to produce line segments and arcs, which are linked to produce a graph describing the character. The third stage, recognition by matching the input character graph to prototype graphs, is described in a companion paper by Rocha and Pavlidis. Finally, secondary classification is applied to break near ties by focusing on discriminating features. The secondary classifier is described in a companion paper by Zhou and Pavlidis. Experimental results on 2000 address blocks supplied by the USPS are presented. We also report experiments on subsampling the data, which indicate that the performance at 100 dpi is very close to that at the original 300 dpi.