Reduce border width on QR Codes generated by ZXing?
I'm using com.google.zxing.qrcode.QRCodeWriter to encode data and com.google.zxing.client.j2se.MatrixToImageWriter to generate the QR Code image. On a 400x400 image, there is about a 52 pixel wide border around the code. I'd like this border to be narrower, maybe 15 pixels, but I don't see anything in the API for doing that. Am I missing something in the documenation? Or would I need to process the image myself?
For reference, here is an example 400x400 QR Code produced with the ZXing library:
Answer
The QR spec requires a four module quiet zone and that's what zxing creates. (See QUIET_ZONE_SIZE in QRCodeWriter.renderResult.)
More recent versions of ZXing allow you to set the size of the quiet zone (basically the intrinsic padding of the QR code) by supplying an int value with the EncodeHintType.MARGIN key. Simply include it in the hints Map you supply to the Writer's encode(...) method, e.g.:
Map<EncodeHintType, Object> hints = new EnumMap<EncodeHintType, Object>(EncodeHintType.class);
hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");
hints.put(EncodeHintType.MARGIN, 2); /* default = 4 */
If you change this, you risk lowering the decode success rate.