Create units_qrcode.markdown

Author: Joe7M

_build/pages/units_qrcode.markdown

@@ -0,0 +1,48 @@
+# QR Code
+
+A QR code (quick-response code) is a two-dimensional image containing a matrix barcode. The code contains data like a string, numbers or
+binary data and can be for example scanned and read out with a smartphone.
+
+## Download the unit
+
+The unit can be downloaded or copy pasted from the [SmallBASIC Github website](https://github.com/smallbasic/smallbasic.plugins/blob/master/units/qrcode.bas).
+Please save the unit in the same directory as your basic file.
+
+## Using the unit
+
+```Freebasic
+import qrcode
+
+color 1, 15
+cls
+
+CreateQRCode("https://smallbasic.github.io")
+
+'### End of main program ######
+
+sub CreateQRCode(text)
+    local bufLen = qrcode.bufferLenForVersion(qrcode.VERSION_MAX)
+    local errCorLvl = qrcode.Ecc_LOW
+    dim qrcode(bufLen)
+    
+    if (!qrcode.encodeText(text, qrcode, errCorLvl, qrcode.VERSION_MIN, qrcode.VERSION_MAX, qrcode.Mask_AUTO, true)) then
+        print "Failed to create QR code"
+    else
+        local size = qrcode.getSize(qrcode)
+        local border = 0
+        local x, y
+        local xs = 5                              ' Pixel size, increase to have bigger pixels
+        local ys = 5                              ' Pixel size, increase to have bigger pixels
+        local xo = (xmax - (size * xs)) / 2
+        local yo = (ymax - (size * xs)) / 2
+
+        for y = 0 to size - 1
+            for x = 0 to  size -1
+                if (qrcode.getModule(qrcode, x, y)) then
+                    rect xo + (xs * x), yo + (ys * y), xo + (xs * (x + 1)), yo + (ys * (y + 1)), 0 filled
+                endif
+            next x
+        next y
+    endif
+end
+```