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

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This commit is contained in:
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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70
lib/input.js
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@@ -238,6 +238,75 @@ function metadata (callback) {
}
}
/**
* Access to pixel-derived image statistics for every channel in the image
* A Promise/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
*
* @example
* const image = sharp(inputJpg);
* image
* .stats()
* .then(function(stats) {
* // stats contains the channel-wise statistics array and the isOpaque value
* })
*
*
* @param {Function} [callback] - called with the arguments `(err, stats)`
* @returns {Promise<Object>|Sharp}
*/
function stats (callback) {
const that = this;
if (is.fn(callback)) {
if (this._isStreamInput()) {
this.on('finish', function () {
that._flattenBufferIn();
sharp.stats(that.options, callback);
});
} else {
sharp.stats(this.options, callback);
}
return this;
} else {
if (this._isStreamInput()) {
return new Promise(function (resolve, reject) {
that.on('finish', function () {
that._flattenBufferIn();
sharp.stats(that.options, function (err, stats) {
if (err) {
reject(err);
} else {
resolve(stats);
}
});
});
});
} else {
return new Promise(function (resolve, reject) {
sharp.stats(that.options, function (err, stats) {
if (err) {
reject(err);
} else {
resolve(stats);
}
});
});
}
}
}
/**
* Do not process input images where the number of pixels (width * height) exceeds this limit.
* Assumes image dimensions contained in the input metadata can be trusted.
@@ -289,6 +358,7 @@ module.exports = function (Sharp) {
// Public
clone,
metadata,
stats,
limitInputPixels,
sequentialRead
].forEach(function (f) {