Symbol-controlled image data reading system

The invention relates to a system for imaging a scene comprising an optical reader and a specially structured symbol configured complementarily with the reader so that when the reader reads the symbol, the reader reads image data in an image data reading region. The image reading instruction symbol of the system may include indicators for controlling various aspects of the image reading process such as the dimension of the image capture region, the relative position of the image reading region. If the image reading instruction symbol is of a type whose actual size, orientation, and distortion can be determined, scaling, orientation, and distortion characteristics determined from the image reading instruction symbol can be used to improve the image reading process. A feedback feature may be included in the reader for indicating to a user whether the reader should be moved in order to improve image reading.