This page contains QR codes in various sizes that link to the home page of this website, the sffiddles.org PR website, and to our Facebook page.
QR codes are a way to encode digital information so that it can be read by an optical reader or camera, similar to the UPC bar code found on almost all commercial products. A very common use of QR codes is to encode the URL of a website so that a user can visit the site simply by pointing their smartphone camera at the QR code, rather than having to manually enter a cumbersome URL. Many QR code scanner smartphone apps are available, and the Android and iPhone camera apps have QR code recognition built into them.
Here is a link to the Wikipedia article on QR codes.
When incorporating a QR code in printed material, one of the first questions that may arise is how big it should be. The required size is a function of how far away the code is expected to be read from and the quality of the printing. If the code is going to be read from a few inches away, such as on a business card or handbill, and the printing is of high quality (e.g., 300dpi on smooth paper), a code approximately 1cm (0.4") square should be fine for most phones. If the printing is lower resolution, or if there is a chance of smearing due to printing or paper quality, a larger size may be required. A good test is simply to try reading the code on a proof sheet with a smartphone.
A close visual inspection comparing the printed results with the ideal image will also help. If the individual black regions in the matrix are clearly separate and identifiable, it will probably be readable. If some of the dots are faint or disappear altogether, or smear into adjacent white space, it will be more difficult to read. The code doesn't have to be perfect; it has redundant information built into it for error correction, but the better the printing the more reliably it will be read.
If a code is to be read from some distance away, such as on a large poster, the code should be correspondingly larger. There are many variables that determine the minimum acceptable size under any given conditions, so the best approach is to try different sizes for the intended application. Printing a code in the proposed size on an inkjet or laser printer is a good way to test it, assuming the print quality of the final product will be at least as good. In one experiment, a 20cm (8") square QR code printed in black on plain white paper was readable at a distance of 7.5m (25') in good lighting using the Android ZXing Barcode Scanner scanner app on a Pixel 2 phone.
Below are links to image files of QR codes for the SFSF websites and our Facebook page. The SVG files are in Scalable Vector Graphics format. These can be resized in a layout tool without creating artifacts. Care must be taken, though, to retain the square aspect ratio. In many tools this can be done by holding the Shift or Ctrl key while dragging a corner control point of the image.
The numbered files are in Portable Network Graphics (PNG) format. These are bitmaps, so scaling these too far may cause objectionable artifacts. The number indicates the size of the image in pixels across one dimension, including a border. The actual size of a printed code will depend on the printing resolution in use. These images may be resized in your page layout program, but the results must be checked for image quality. For best results, it is recommended that you start with an image that is close to the desired size.
If possible, avoid any process that includes converting these images into JPEG format. JPEG is designed to work with natural images, which do not have the absolutely abrupt edges of computer-generated text, line art, and other binary images. The result is that such images that have been subjected to JPEG compression will acquire fuzzy artifacts on the black/white transitions. This can be minimized by setting the quality level to maximum during compression, but it is generally better to avoid JPEG and use PNG, GIF, or SVG formats.
|URL||Image Size (pixels square)|
Zip file containing all of the above: qr_codes.zip
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