This chapter describes techniques for improvement of the performance and detection rate.
Before the TIS Barcode SDK is used in daily routine, it is highly recommended to perform a test using multiple sample barcodes under regular production conditions.
For best readability, 1D barcodes require at least 2 pixels per element. 2D barcodes require at least 4 pixels for each module.
The minimum width of barcode modules is specified in mil (1 mil ~ 0.001 inch / 0.0254 mm).
Depending on the barcode symbologies and the character pitch, the scanner resolution for successful barcode reading can vary between 75 dpi and 600 dpi. The following table shows the recommended barcode sizes that ensure reliable and proper decoding depending on the camera system's DPI.
In addition to scanner resolution and barcode width, reliable recognition also depends on other factors such as quality of printer and paper, scanner settings, barcode type, height and width of barcode as well as the number of characters in the barcode.
When cameras are used for image acquisition, light exposure, sharpness, distortion and image data compression also influence the quality of the detection results. Monochrome cameras are generally preferable.
In general, it is always better to improve the quality of an image by altering the image acquisition than improving the image afterwards.
It is possible that barcdoes will not be immediately recognized by the TIS Barcode SDK. In most cases, the reasons for unsuccessful recognition are errors which can easily be corrected:
Inappropriate scanner settings
If the resolution of the acquired images is too low, fine bars/modules can not be separated correctly. Thus the program cannot recognize the gaps and the numeral cannot be decoded.
If the scan is too dark or too bright, the bars enlarge which makes thin gaps disappear or bars which are necessary for the recognition can be missing. .
When processing a very large number of barcdoes, the performance can be increased by restricting the orientation tolerance, limiting the number of expected barcodes per image or reducing the number of scanlines used for decoding.
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