I'll create a professional QR code and barcode for $ 5 for you

I will create a professional QR code and barcode for you

Hello customers,

I would like to provide the QR codes for different customer needs. I will offer different types of QR codes at a reasonable price.I can provide QR codes : –

  • URL
  • TEXT
  • MAIL
  • SMS
  • wireless Internet access

Linear Algebra – Why should a QR decomposition not be possible for a "fat" matrix?

The Wikipedia article on QR decomposition reads:

In general, we can factorize a complex m × n matrix A with m ≥ n as the product of an m × m unit matrix Q and an m × n upper triangular matrix R.

I was just wondering what would happen if I tried to split a matrix with more columns than rows. I would only follow Gram-Schmidt (described in the same Wikipedia article) until I have one $ m times m $ orthonormal matrix. Then the remaining columns of $ R $(considering the original $ c_j $) would be easy $ Q ^ {- 1} c_j $,

Cell Phone – Do People Use QR Codes?

TL; DR: Not The currently popular, but could be so in the future. In your case I would look for an additional option if possible.

To edit: Because of RonJohn's comment and the many people who agreed, I decided to rebuild the charts in a "real" way so that the numbers look less manipulative.

Scanova.io quotes some surveys over the years and claims that they are on the rise:

In 2014, Adobe Systems conducted a study on the use of QR code over a period of three months. The study included four countries – Germany, France, the United Kingdom and the United States.

Official study overview:

New chart created in Excel:
Diagram of the use of QR codes in percent per country

According to a recent survey by Statistia, in the US alone, by 2020, an estimated 11 million households will scan a QR code. This is an increase of an estimated 9.76 million scans in 2018.

Official study overview:

New chart created in Excel:
Diagram of the use of QR codes in millions of US households

They also show how widespread it is in some large Asian countries, especially in China:

WeChat – which is mainly used in China – has obsessed the nation with QR codes in recent years. The Chinese scan QR codes to make payments, retrieve information, authenticate, use offers, and virtually any other use case.

Personally, I am not too convinced. I hardly ever see QR codes being used (living in a western EU country), not people I know, and not in public.

This mediag.com article makes a good point about it:

Many people hear "QR Code" and think, "2011 means, and they want their marketing tactics back." They start to reach a plateau and even celebrate a comeback since their huge decline in popularity in 2014-2016.

So it seems that they are not very popular at the moment, but could it be again in the future? Hard to tell. However, for your use case, this means it would not be a bad idea to have an alternative to it (as not everyone has a QR code scanner app installed).

Example from real life

Interestingly enough, I got that in my mail today after saying that I never see her here 🙂

Enter image description here

This is a really good example, as you can see clearly There are two possibilities, As Bergi said in his comment on the question, the QR-Link should also be provided in a readable form.

Transactions – QR to pay more than one address?

I know that I can generate syntax for a payment QR code like this:

bitcoin: xxxaddressxxx? lable = reason & amount = 0.051

that pays (to) 1 address! However, I want to know if I can scan a QR that creates a TX that gets paid to two addresses

(Can I add more than one address?)


Bitcoin:[xxxaddressxxx1,xxxaddressxxx2]? lable = reason & amount =[0.05,0.001]

So the addresses get sums relative to the array positions

qrcode – Will the Bitcoin QR Code Generator be hacked by BTCFrog?

The following URL is self-explanatory. An attempt is made to generate a QR code requesting 0.005 BTC at the indicated address


This generates the following QR code

Enter image description here

If this QR code is scanned with a purse of your choice, the recipient address will change to something else! The address is clearly owned by someone and has multiple transactions.

Is it hacked or am I doing something seriously wrong?

How to do a second activity on Android after reading a qr code?

I have a problem launching the second activity on Android because I have a program that reads qr codes, and in this sentence I have the following

if (URLUtil.isValidUrl (token)) {// token contains reading the code
Intent browserIntent = new Intent (Intent.ACTION_VIEW,
Uri.parse (token));
startActivity (browserIntent);
// This part works properly
} else {

try it
Intent act2 = new intent (MainActivity.this, Activity2.class);
startActivity (act2);
// This part does not work, does not check the box, it closes the app
catch (exception e) {
Toast.makeText (MainActivity.this,
e.getMessage (), Toast.LENGTH_SHORT) .show ();

Please help
Thank you

qrcode – Bitcoin QR code for a product sold in stores

Setting a Bitcoin payment address (in QR code format or otherwise) is generally not a way to accept Bitcoin for a sale. There are very basic vulnerabilities, such as: For example, someone may swap the payment address shown on your product, and so on. Trying to use the same address for each product is bad for privacy and makes backend billing difficult.

Accepting Bitcoin for payments is best done with a Bitcoin payment processor such as BTCPayServer (an open source project). On a small scale, you can even manually process payments at checkout. In both cases, customers will see a payment address during the payment process. Not one payment address per product.

Web QR code check-in / out system for devices

So I'm developing a device check-in / out (smartphone / tablet) that tracks the current status (in / out) of a device and who's currently in a business.

My main options are currently QR code or RFID, which leads to QR codes for cost reasons.
The main problem I have to solve is how the qr code updates the status. I was thinking of somehow updating a Google Sheet when a device is scanned or scanned. With QR codes, I know that they can only contain limited data scanned and are usually reserved mainly for web links and so on

Does anyone know of a reasonable way to update the status this way, or would RFID be a better option for me?