| Requirements | exec() function and that the webserver has permission to run `cwebp` binary (either found in system path, or a precompiled version supplied with this library) |
|---|
| Performance | ~40-120ms to convert a 40kb image (depending on *method* option) |
|---|
| Reliability | No problems detected so far! |
|---|
| Availability | According to ewww docs, requirements are met on surprisingly many webhosts. Look here for a list |
|---|
| General options supported | All (`quality`, `metadata`, `lossless`) |
|---|
| Extra options | `method` (0-6)
`use-nice` (boolean)
`try-common-system-paths` (boolean)
`try-supplied-binary-for-os` (boolean)
`autofilter` (boolean)
`size-in-percentage` (number / null)
`command-line-options` (string)
`low-memory` (boolean) |
|---|
[cwebp](https://developers.google.com/speed/webp/docs/cwebp) is a WebP conversion command line converter released by Google. Our implementation ships with precompiled binaries for Linux, FreeBSD, WinNT, Darwin and SunOS. If however a cwebp binary is found in a usual location, that binary will be preferred. It is executed with [exec()](http://php.net/manual/en/function.exec.php).
In more detail, the implementation does this:
- It is tested whether cwebp is available in a common system path (eg `/usr/bin/cwebp`, ..)
- If not, then supplied binary is selected from `Converters/Binaries` (according to OS) - after validating checksum
- Command-line options are generated from the options
- If [`nice`]( https://en.wikipedia.org/wiki/Nice_(Unix)) command is found on host, binary is executed with low priority in order to save system resources
- Permissions of the generated file are set to be the same as parent folder
### Cwebp options
The following options are supported, besides the general options (such as quality, lossless etc):
| Option | Type | Default |
| -------------------------- | ------------------------- | -------------------------- |
| autofilter | boolean | false |
| command-line-options | string | '' |
| low-memory | boolean | false |
| method | integer (0-6) | 6 |
| near-lossless | integer (0-100) | 60 |
| size-in-percentage | integer (0-100) (or null) | null |
| rel-path-to-precompiled-binaries | string | './Binaries' |
| size-in-percentage | number (or null) | is_null |
| try-common-system-paths | boolean | true |
| try-supplied-binary-for-os | boolean | true |
| use-nice | boolean | false |
Descriptions (only of some of the options):
#### the `autofilter` option
Turns auto-filter on. This algorithm will spend additional time optimizing the filtering strength to reach a well-balanced quality. Unfortunately, it is extremely expensive in terms of computation. It takes about 5-10 times longer to do a conversion. A 1MB picture which perhaps typically takes about 2 seconds to convert, will takes about 15 seconds to convert with auto-filter. So in most cases, you will want to leave this at its default, which is off.
#### the `command-line-options` option
This allows you to set any parameter available for cwebp in the same way as you would do when executing *cwebp*. You could ie set it to "-sharpness 5 -mt -crop 10 10 40 40". Read more about all the available parameters in [the docs](https://developers.google.com/speed/webp/docs/cwebp)
#### the `low-memory` option
Reduce memory usage of lossy encoding at the cost of ~30% longer encoding time and marginally larger output size. Default: `false`. Read more in [the docs](https://developers.google.com/speed/webp/docs/cwebp). Default: *false*
#### The `method` option
This parameter controls the trade off between encoding speed and the compressed file size and quality. Possible values range from 0 to 6. 0 is fastest. 6 results in best quality.
#### the `near-lossless` option
Specify the level of near-lossless image preprocessing. This option adjusts pixel values to help compressibility, but has minimal impact on the visual quality. It triggers lossless compression mode automatically. The range is 0 (maximum preprocessing) to 100 (no preprocessing). The typical value is around 60. Read more [here](https://groups.google.com/a/webmproject.org/forum/#!topic/webp-discuss/0GmxDmlexek). Default: 60
#### The `size-in-percentage` option
This option sets the file size, *cwebp* should aim for, in percentage of the original. If you for example set it to *45*, and the source file is 100 kb, *cwebp* will try to create a file with size 45 kb (we use the `-size` option). This is an excellent alternative to the "quality:auto" option. If the quality detection isn't working on your system (and you do not have the rights to install imagick or gmagick), you should consider using this options instead. *Cwebp* is generally able to create webp files with the same quality at about 45% the size. So *45* would be a good choice. The option overrides the quality option. And note that it slows down the conversion - it takes about 2.5 times longer to do a conversion this way, than when quality is specified. Default is *off* (null)
#### final words on cwebp
The implementation is based on the work of Shane Bishop for his plugin, [EWWW Image Optimizer](https://ewww.io). Thanks for letting us do that!
See [the wiki](https://github.com/rosell-dk/webp-convert/wiki/Installing-cwebp---using-official-precompilations) for instructions regarding installing cwebp or using official precompilations.
## vips
| Requirements | Access to a server with [webp-convert-cloud-service](https://github.com/rosell-dk/webp-convert-cloud-service) installed, cURL and PHP >= 5.5.0 |
|---|
| Performance | Depends on the server where [webp-convert-cloud-service](https://github.com/rosell-dk/webp-convert-cloud-service) is set up, and the speed of internet connections. But perhaps ~1000ms to convert a 40kb image |
|---|
| Reliability | Great (depends on the reliability on the server where it is set up) |
|---|
| Availability | Should work on almost any webhost |
|---|
| General options supported | All (`quality`, `metadata`, `lossless`) |
|---|
| Extra options (old api) | `url`, `secret` |
|---|
| Extra options (new api) | `url`, `api-version`, `api-key`, `crypt-api-key-in-transfer` |
|---|
[wpc](https://github.com/rosell-dk/webp-convert-cloud-service) is an open source cloud service. You do not buy a key, you set it up on a server, or you set up [the Wordpress plugin](https://wordpress.org/plugins/webp-express/). As WebPConvert Cloud Service itself is based on WebPConvert, all options are supported.
To use it, you need to set the `converter-options` (to add url etc).
#### Example, where api-key is not crypted, on new API:
```php
WebPConvert::convert($source, $destination, [
'max-quality' => 80,
'converters' => ['cwebp', 'wpc'],
'converter-options' => [
'wpc' => [
'api-version' => 1, /* from wpc release 1.0.0 */
'url' => 'http://example.com/wpc.php',
'api-key' => 'my dog is white',
'crypt-api-key-in-transfer' => false
]
]
));
```
#### Example, where api-key is crypted:
```php
WebPConvert::convert($source, $destination, [
'max-quality' => 80,
'converters' => ['cwebp', 'wpc'],
'converter-options' => [
'wpc' => [
'api-version' => 1,
'url' => 'https://example.com/wpc.php',
'api-key' => 'my dog is white',
'crypt-api-key-in-transfer' => true
],
]
));
```
In 2.0, you can alternatively set the api key and urls through through the *WPC_API_KEY* and *WPC_API_URL* environment variables. This is a safer place to store it.
To set an environment variable in Apache, you can use the `SetEnv` directory. Ie, place something like the following in your virtual host / or .htaccess file (replace the key with the one you purchased!)
```
SetEnv WPC_API_KEY my-dog-is-dashed
SetEnv WPC_API_URL https://wpc.example.com/wpc.php
```
#### Example, old API:
```php
WebPConvert::convert($source, $destination, [
'max-quality' => 80,
'converters' => ['cwebp', 'wpc'],
'converter-options' => [
'wpc' => [
'url' => 'https://example.com/wpc.php',
'secret' => 'my dog is white',
],
]
));
```
## ewww