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Add pixel-derived image statistics via vips_stats (#915)

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Rahul Nanwani
2017-12-09 16:47:48 +05:30
committed by Lovell Fuller
parent dfaa39fa5d
commit d6aee8e5ba
9 changed files with 971 additions and 0 deletions
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docs/api-input.md
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@@ -67,6 +67,42 @@ image
Returns **([Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)<[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)> | Sharp)**
## stats
Access to pixel-derived image statistics for every channel in the image
A Promises/A+ promise is returned when `callback` is not provided.
- `channels`: Array of channel statistics for each channel in the image. Each channel statistic contains
- `min` (minimum value in the channel)
- `max` (maximum value in the channel)
- `sum` (sum of all values in a channel)
- `squaresSum` (sum of squared values in a channel)
- `mean` (mean of the values in a channel)
- `stdev` (standard deviation for the values in a channel)
- `minX` (x-coordinate of one of the pixel where the minimum lies)
- `minY` (y-coordinate of one of the pixel where the minimum lies)
- `maxX` (x-coordinate of one of the pixel where the maximum lies)
- `maxY` (y-coordinate of one of the pixel where the maximum lies)
- `isOpaque`: Value to identify if the image is opaque or transparent, based on the presence and use of alpha channel
**Parameters**
- `callback` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)?** called with the arguments `(err, metadata)`
**Examples**
```javascript
const image = sharp(inputJpg);
image
.stats()
.then(function(stats) {
// stats contains the channel-wise statistics array and the isOpaque value
})
```
Returns **([Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)<[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)> | Sharp)**
## limitInputPixels
Do not process input images where the number of pixels (width _ height) exceeds this limit.