Question
What accuracy can I expect from the barcode check in the Viewer or the Inspect Barcode task?
Answer
The expected accuracy depends on the rendering resolution of the image. See below table for an estimation on the accuracy of the measurement:
Automation Engine Viewer ( not prepared ) | Automation Engine Viewer ( prepared at 600 ppi ) | Inspect Barcode task ( at 300 ppi ) | Inspect Barcode task ( at 600 ppi ) | |
|---|---|---|---|---|
| Default Settings | Prepared 600 ppi | 300 ppi | 600 ppi | |
| Average deviation (mm) | 0.0051 mm | 0.0035 mm | 0.0018 mm | 0.0032 mm |
| Max deviation (mm) | 0.0300 mm | 0.0125 mm | 0.0110 mm | 0.0100 mm |
The easiest way to improve the accuracy is to increase the resolution. For the Automation Engine Viewer, this can be done by preparing the file and setting the resolution to f.e. 600 ppi. In the 'Inspect Barcode' task, you can do this by setting a resolution of f.e. 600 ppi i.s.o. the default of 300 ppi.
Be aware that a higher resolution always needs more memory. Setting a resolution too high can cause performance issues or out-of-memory errors.
When you see the task failing with "ERROR: Image would be too large to raster", then please see this KB:
Technical Explanation
At 1200 ppi, the narrowest bar should be 10.87 pixels (0.00906*1200). If the bar is represented by 11 pixels, that’s an error of 0.13 pixels or 0.0028 mm for bar width reduction ('BWR'). The error is in that case then drastically reduced and does not significantly affect the result of calculating the BWR.
Another potential cause of issue with accuracy of BWR is the software's edge detector accuracy to properly locate the barcode bar transitions. In particular on scanned images with poor contrast, a precision of 0.1 pixel or less is required. The BWR accuracy in the AE Viewer or the 'Inspect Barcode' task is listed in the table below:
After calculating the BWR, the value is rounded off to 2 decimals behind the comma (f.e.: 0.0453 mm will be shown as 0.05 mm).
The main issue with BWR accuracy comes from the accuracy of PDF file rasterization.
- Example: On an EAN/UPC barcode, the nominal width value of the X-dimension (narrowest bar) is 0.013 inch or 0.33 mm (1 inch = 25.4 mm). Assuming there is a 0.1 mm BWR , the narrowest bar width should be 0.00906 inch or 0.23 mm. At 300 dpi, this corresponds to 2.72 pixels (0.00906*300). When the the rasterizer represents the narrowest bar with 3 pixels, then the BWR error is 0.28 pixels or 0.024 mm (0.28*25.4/300).
- An accurate representation for the narrowest bar should be a bar with 2 black pixels and the third pixel set to a gray scale value of 71 as shown below:
| Article information | |
|---|---|
| Applies to | Automation Engine 12.x and newer |
| Created |
|
| Last revised | |
| Author | GDM |
| Case Number | |