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81 lines
4.7 KiB
Markdown
81 lines
4.7 KiB
Markdown
# Performance considerations
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Generating a QR Code is not a trivial task - it is a combination of countless complex mathematical operations on top of rendering the output.
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This library seeks not to be the fastest QR Code generator, but instead to provide flexibility and user friendlyness,
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which in turn comes with a slight performance cost.
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## Version
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The [version of the QR symbol](./Terminology.md#version) is one of the major performance factors as it
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determines the size of the symbol and therefore the amount of data that can be stored. Iterating over the internal
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representation of the matrix takes more time with increasing size and the internals iterate over the matrix a LOT.
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Because of that, you want to select the smallest possible version for the given data of course, which the encoder does by default.
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However, sometimes the possibly varying size of the symbol may not be desired and you want to choose a fixed size, in which case
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you should determine the maximum size of the input data and choose a version that fits.
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## Ecc level
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Another factor is the [ECC level](./Terminology.md#ecc-error-correction-coding) that determines the error correction capacity. The default setting is the lowest capacity (L, 7%)
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which allows the highest amount of data to be stored and which is good enough for e.g. on-screen display or poster prints.
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ECC level H on the other hand allows for up to 30% error correction capacity, which is great for "high risk" applications such as prints on mail.
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With increasing error correction capacity, the maximum amount of data a symbol can hold decreases, and a higher version number may be necessary.
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## Data mode
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By default, the encoder auto-detects the best [mode for data encoding](Terminology.md#mode) (numeric, alphanumeric, kanji, hanzi or 8-bit binary)
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and depending on the length of the given data, the detection costs an increasing amount of time. To circumvent this,
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you can call one of the "add segment" methods on the `QRCode` instance, for example: `$qrcode->addByteSegment($data)`.
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Generally, using 8-bit binary mode (or just "byte mode") is the fast and fail-safe mode for any kind of data, and with
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[ECI](https://en.wikipedia.org/wiki/Extended_Channel_Interpretation) it even offers support for character sets other than UTF-8.
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So, unless you want to fit a large amount of japanese or chinese characters into a QR symbol of a certain version,
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encoding those characters as 3 or 4 byte UTF-8 may still be faster in 8-bit byte than in the "compressed" 13-bit double byte modes.
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## Mask pattern
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[Evaluating the QR symbol](./Terminology.md#data-masking) in order to pick the right [mask pattern](./Terminology.md#mask-pattern)
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is a complex and costly operation that is necessary to ensure the symbol is readable. Although [there is an option](../Usage/Configuration-settings.md#maskpattern)
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to override the evaluation and manually set a mask pattern, this is not recommended unless you know exactly what you're doing
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as it can render a QR symbol unreadable.
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The table below shows the performance impact (in miliseconds) of the mask pattern evaluation for select versions, the times may vary between systems.
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| version | time (ms) |
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|---------|----------:|
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| **1** | 2.285 |
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| **5** | 5.867 |
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| **10** | 12.737 |
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| **20** | 34.045 |
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| **30** | 64.914 |
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| **40** | 107.027 |
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## Output
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Output rendering depends heavily on the size of the QR matrix, the desired type and the underlying libraries and/or PHP extensions.
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Especially the rendering of raster images through GD or ImageMagick can be very slow, depending on [the scale setting](../Usage/Configuration-settings.md#scale),
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filters and image type.
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Below a comparison of the performance for the several built-in output classes (times in miliseconds, scale = 5):
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| | v5 | v10 | v20 | v30 | v40 |
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|-------------------|-------:|-------:|--------:|--------:|--------:|
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| **QRMarkupSVG** | 3.732 | 8.645 | 21.127 | 43.753 | 73.885 |
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| **QRMarkupHTML** | 0.522 | 1.308 | 2.761 | 5.201 | 9.572 |
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| **QRGdImageBMP** | 5.998 | 12.541 | 32.336 | 62.842 | 106.482 |
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| **QRGdImageGIF** | 3.427 | 6.817 | 17.925 | 35.136 | 57.477 |
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| **QRGdImageJPEG** | 2.284 | 4.882 | 12.097 | 23.862 | 40.226 |
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| **QRGdImagePNG** | 4.523 | 9.377 | 26.207 | 49.066 | 82.074 |
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| **QRGdImageWEBP** | 8.211 | 17.367 | 47.095 | 91.378 | 150.288 |
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| **QRStringJSON** | 0.043 | 0.066 | 0.158 | 0.301 | 0.492 |
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| **QRStringText** | 0.229 | 0.387 | 0.952 | 1.759 | 3.045 |
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| **QRImagick** | 37.694 | 68.808 | 172.962 | 325.085 | 529.897 |
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| **QRFpdf** | 6.578 | 12.466 | 33.021 | 61.198 | 100.059 |
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| **QREps** | 1.269 | 2.694 | 6.933 | 14.181 | 25.886 |
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