On 09/03/2024 19:08, hw wrote:
On Fri, 2024-03-08 at 23:21 +0700, Max Nikulin wrote:On 08/03/2024 12:35, hw wrote:On Thu, 2024-03-07 at 23:15 -0500, Jeffrey Walton wrote:I have a USB thermal printer for the shipping labels, <https://www.amazon.com/gp/product/B08V28J3JS>.This printer has only 300dpi. If you print QR-codes on it make sure you can scan them: they have to be large enough or get you an unscanable smear.I believed that 300dpi is high enough resolution for QR-codes of reasonable size if source image has proper quality. On the other hand, if possible, it is better to scale QR-codes to match some whole factor of printer pixel size.What do you consider a 'reasonable size'?
Looking at a QR code likely having ~75 pixels per inch I find it unreasonably small for delivery labels. I am in doubts if its redundancy is high enough to reliably recognize it if it would be scratched during delivery. Another limitation may be stability of optics in scanners in respect to labels. This one is printed using a laser printer with resolution at least 600 dpi. Each QR code pixel has still 4x4 printer dots in the case of 300dpi, so when image is properly aligned, printer quality is not an issue.
There is no source image other than whatever LaTeX creates. I can specify the size of the QR-code. Other than that, how do you apply scaling?
I am unsure what particular QR code generator do you use and what is the format of QR codes. Is it raster or vector image? Specify size that makes QR code pixels having whole number of printer pixels.
"Fit to page" or "fit to printable area" in printer options may make an image blurry. In the case of low input image resolution, upscaling method suitable for photos may make QR code blurry. However consistent configuration should make QR codes sharp.