The present disclosure relates to advanced image signal processing technology including: i) rapid localization for machine-readable indicia including, e.g., 1-D and 2-D barcodes; and ii) barcode reading and decoders. One claim recites: an image processing method comprising: obtaining 2-dimensional (2D) image data representing a 1-dimensional (1D) barcode within a first image area; generating a plurality of scanlines across the first image area; for each of the plurality of scanlines, synchronizing the scanline, including decoding an initial set of numerical digits represented by the scanline, in which said synchronizing provides a scale estimate for the scanline; using a path decoder to decode remaining numerical digits within the scanline, the path decoder decoding multiple numerical digits in groups, in which the scale estimate is adapted as the remaining numerical digits are decoded; and providing decoded numerical digits as an identifier represented by the scanline. Of course, other combinations and claims are described within the present disclosure.