70 lines
3.1 KiB
Markdown
70 lines
3.1 KiB
Markdown
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# QR Code Generator Module
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| Since | Origin / Contributor | Maintainer | Source |
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| :----- | :-------------------- | :---------- | :------ |
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| 2018-10-20 | https://github.com/nayuki/QR-Code-generator.git integrated by [Tom Sutcliffe](https://github.com/tomsci) | [Tom Sutcliffe](https://github.com/tomsci) | [qrcodegen.c](../../../components/modules/qrcodegen.c)|
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This module wraps the [QR Code](https://en.wikipedia.org/wiki/QR_code) Generator API written in C by https://github.com/nayuki/QR-Code-generator.git for producing a QR Code.
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## qrcodegen.encodeText()
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Generates a QR Code from a text string. In the most optimistic case, a QR Code at version 40 with low ECC can hold any UTF-8 string up to 2953 bytes, or any alphanumeric string up to 4296 characters, or any digit string up to 7089 characters.
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#### Syntax
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`qrcodegen.encodeText(text, [options])`
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#### Parameters
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- `text` The text or URL to encode. Should be UTF-8 or ASCII.
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- `options` An optional table, containing any of:
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- `minver` the minimum version according to the QR Code Model 2 standard. If not specified, defaults to `1`.
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- `maxver` the maximum version according to the QR Code Model 2 standard. If not specified, defaults to `40`. Specifying a lower maximum version reduces the amount of temporary memory the function requires, so it can be worthwhile to specify a smaller value if you know the `text` will fit in a lower-version QR Code.
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- `ecl` the error correction level in a QR Code symbol. Higher error correction produces a larger QR Code. One of:
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- `qrcodegen.LOW` (default if not specified)
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- `qrcodegen.MEDIUM`
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- `qrcodegen.QUARTILE`
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- `qrcodegen.HIGH`
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- `mask` the mask pattern used in a QR Code symbol. An integer 0-7, or `qrcodegen.AUTO` (the default).
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- `boostecl` defaults to false.
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#### Returns
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The QR Code, encoded as a string. Use `qrcodegen.getSize()` and `qrcodegen.getPixel()` to extract data from the result. If the text cannot be represented within the given version range (for example it is too long) then `nil` is returned.
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#### Example
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```lua
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qrcode = qrcodegen.encodeText("https://nodemcu.readthedocs.io/", {minver=1, maxver=4})
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print("Size:", qrcodegen.getSize(qrcode))
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```
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## qrcodegen.getSize()
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#### Syntax
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`qrcodegen.getSize(qrcode)`
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#### Parameters
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- `qrcode` a QR Code string, as returned by `qrcodegen.encodeText()`.
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#### Returns
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Returns the side length in pixels of the given QR Code. The result is in the range [21, 177].
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## qrcodegen.getPixel(qrcode, x, y)
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Get the color of the pixel at the given coordinates of the QR Code. `x` and `y` must be between `0` and the value returned by `qrcodegen.getSize()`.
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#### Parameters
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- `qrcode` a QR Code string, as returned by `qrcodegen.encodeText()`.
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- `x`
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- `y`
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#### Returns
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`true` if the given pixel is black, `false` if it is white.
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#### Example
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```lua
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qrcode = qrcodegen.encodeText("https://nodemcu.readthedocs.io/", {maxver=4})
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size = qrcodegen.getSize(qrcode)
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for y = 0, size-1 do
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local row = {}
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for x = 0, size-1 do
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row[x + 1] = qrcodegen.getPixel(x, y) and "*" or " "
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end
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print(table.concat(row))
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end
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```
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