The disclosure describes pattern recognition detectors and software used to detect objects in image streams. The detectors operate on streams of image data, making them suitable for detecting certain types of objects in documents and images passed between processes and devices. For instance, the streaming mode detectors operate in printer drivers on streams of image data being passed to a printer. Also, the streaming mode detectors operate in scanner drivers on streams of image data being passed from a scanner. The disclosure describes pattern detectors for shapes with complex features as well as objects comprised of many smaller shapes. The disclosure also describes novel raster line and edge tracing pattern techniques.