A coordinate system is built based on the barcode in its rectified (de-skewed) form. The origin is the center of the barcode, and the x-axis is set toward the right, from the barcode's point of view. The unit module width of the barcode is the unit for x. Similarly, the y-axis is set toward the up direction. The unit for the y-axis is specified via the parameter IDC Aspect. This is the aspect ratio of a thin bar or space - the barcode's height is divided by this value to get this unit. Set IDC Aspect to zero to automatically calculate the aspect ratio. The barcode can be of different sizes for the same form, as long as the center of the barcode is the same when the barcode's length changes.
From this coordinate system, the IDC area is determined using four parameters: offsets in x and y (IDC X Coordinate, IDC Y Coordinate) to the region's top-left corner, and width and height IDC Width, IDC Height).
If the capture area is relatively large as compared to the barcode area, the calculation to obtain the capture area is prone to significant errors. A recommended solution is to enclose the form with a single black-lined rectangular border (a box), which is not in contact with any other line on the outside of the form (although it can be connected to lines on the inside of the form). When the IDC Find Box Outline is set, the firmware searches for the box, and does not decode if any edges are broken (such as by a protruding thumb).
The IDC Zoom Limit parameter controls the quality of the captured form. The IDC firmware rejects capturing a form unless the width is at least the IDC Zoom Limit percentage of the IDC Width parameter. For example, if IDC Zoom Limit is set to 100 and IDC Width Limit is set to 150, the form must be at least 300 pixels wide before it is captured (each unit module is scaled to two pixels).
The IDC Maximum Rotation parameter controls the maximum rotation any edge of the form can have in relation to the scanner's horizontal or vertical axis.
