The main requirement is for each black or white bar in a barcode to be clearly visible on the image. All barcodes have at least 2 sizes of bar and the image needs to be of high enough quality to show this. For example, a Code 39 barcode consists of 9 bars per character, of which 3 must be wide and 6 must be narrow. The wide bars should be around 2.5 times the size of the narrow bars – but for simplicity we will say 2 times the size. This means that each character needs at least 12 pixels in an image. This assumes that each pixel in the image lies either entirely in a black bar or entirely in a white bar. In practise, this isn’t possible and so the resolution should allow around 24 pixels per character.<\/p>\n
So, to encode a string of 10 characters (not including the start and stop *) you will need at around 288 pixels. If the barcode is 1 inch wide on the paper then you will need to scan at a resolution of around 300 DPI. If the barcode is 2 inches wide then you will need to scan at a resolution of around 200 DPI.<\/p>\n
Some types of barcode have more than 2 widths of bar and a higher resolution still will be needed to ensure that the different widths can be distinguished on the image.<\/p>\n
As for barcode height – if you have a very wide barcode then you need to ensure that it is high enough to cope with any skewing that takes place when the image is scanned.<\/p>\n
In summary – the success of a project can depend on specifying the correct barcode size and image resolution.<\/p>\n
| Barcode Type<\/th>\n | Number of Characters<\/th>\n | Minimum Number of Pixels (approx)<\/th>\n<\/tr>\n |
|---|---|---|
| Code 39<\/td>\n | 10<\/td>\n | 288<\/td>\n<\/tr>\n |
| Code 2 of 5 (interleaved)<\/td>\n | 10<\/td>\n | 156<\/td>\n<\/tr>\n |
| Code 128 (code set A)<\/td>\n | 10<\/td>\n | 286<\/td>\n<\/tr>\n |
| Code 128 (code set B)<\/td>\n | 10<\/td>\n | 286<\/td>\n<\/tr>\n |
| Code 128 (code set C)<\/td>\n | 10<\/td>\n | 176<\/td>\n<\/tr>\n |
| EAN-13<\/td>\n | 13<\/td>\n | 166<\/td>\n<\/tr>\n |
| EAN-8<\/td>\n | 8<\/td>\n | 118<\/td>\n<\/tr>\n |
| UPC-A<\/td>\n | 12<\/td>\n | 166<\/td>\n<\/tr>\n |
| UPC-E<\/td>\n | 8<\/td>\n | 102<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n","protected":false},"excerpt":{"rendered":" The main requirement is for each black or white bar in a barcode to be clearly visible on the image. All barcodes have at least 2 sizes of bar and the image needs to be of high enough quality to show this. For example, a Code 39 barcode consists of 9 bars per character, of<\/p>\n |