Jeroen Ooms

The latest version of the [opencv R
package](https://ropensci.r-universe.dev/opencv) can detect and decode
QR codes!

::: {.highlight}
``` {.chroma tabindex="0"}
# Install latest opencvinstall.packages("opencv", repos = "https://ropensci.r-universe.dev")
```
:::

There are two ways of using this: the
[`ocv_qr_detect`](https://docs.ropensci.org/opencv/reference/qrcode.html)
function tries to find the QR in an image file. It returns either a text
string or NULL (if no QR code was found in the image):

::: {.highlight}
``` {.chroma tabindex="0"}
img <-  opencv::ocv_read('https://jeroen.github.io/images/qrtest.jpg')opencv::ocv_qr_detect(img)## https://www.r-project.org
```
:::

Alternatively if your laptop has a camera, you can use R as a true QR
code scanner! The
[`qr_scanner`](https://docs.ropensci.org/opencv/reference/qrcode.html)
function starts the camera device and filters the video stream through
the above `ocv_qr_detect` until a QR code has been detected.

::: {.highlight}
``` {.chroma tabindex="0"}
# This requires a cameratxt <- opencv::qr_scanner()
```
:::

By default, both `ocv_qr_detect` and `qr_scanner` return the text value
of the decoded QR code. But both functions also have an option
`draw = TRUE` which will instead return an annotated image with the
position and value of the QR drawn into the image, and qr text value as
an attribute.

::::: {.gallery .caption-position-bottom .caption-effect-slide .hover-effect-zoom .hover-transition itemscope="" itemtype="http://schema.org/ImageGallery"}
::: {.box}
<figure itemprop="associatedMedia" itemscope=""
itemtype="http://schema.org/ImageObject">
<div class="img" style="background-image: url(&#39;input.jpg&#39;);">
<img src="input.jpg" itemprop="thumbnail"
alt="Input photo which includes a QR code" />
</div>
<a href="input.jpg" itemprop="contentUrl" aria-disabled="true"></a>
</figure>
:::

::: {.box}
<figure itemprop="associatedMedia" itemscope=""
itemtype="http://schema.org/ImageObject">
<div class="img" style="background-image: url(&#39;output.jpg&#39;);">
<img src="output.jpg" itemprop="thumbnail"
alt="Annotated output which shows the input plus highlighted QR area" />
</div>
<a href="output.jpg" itemprop="contentUrl" aria-disabled="true"></a>
</figure>
:::
:::::

## Generating QR codes in R

There exists another package on CRAN called
[qrcode](https://thierryo.github.io/qrcode/) (currently maintained by
Thierry Onkelinx) which can generate most types of QR codes using R
graphics, which is super cool.

We can combine the two packages to roundtrip text to QR codes in R:

::: {.highlight}
``` {.chroma tabindex="0"}
## generate a qr code imagepng("qr-test.png")plot(qrcode::qr_code("This is a test!"))dev.off()# Verify that we can read it:ocv_qr_detect(ocv_read('qr-test.png'))## [1] "This is a test!"
```
:::

So this provides a quick way to exchange small blobs of information
between computers running R, without the need for any network
connection.


The latest version of the opencv R package can detect and decode QR codes! # Install latest opencvinstall.packages("opencv", repos = "https://ropensci.r-universe.dev")  There are two ways of using this: the ocv_qr_detect function tries to find the QR in an image file.

Messaggi di Rogue Scholar

Scanning QR codes in R