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Add greyscale option to threshold operation (#480)

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Matt Hirsch
2016-07-03 14:32:07 -04:00
committed by Lovell Fuller
parent 4b98dbb454
commit 85f20c6e1b
8 changed files with 55 additions and 3 deletions
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docs/api.md
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@@ -391,12 +391,14 @@ When a `sigma` is provided, performs a slower, more accurate sharpen of the L ch
* `flat`, if present, is a Number representing the level of sharpening to apply to "flat" areas, defaulting to a value of 1.0.
* `jagged`, if present, is a Number representing the level of sharpening to apply to "jagged" areas, defaulting to a value of 2.0.
#### threshold([threshold])
#### threshold([threshold], [options])
Converts all pixels in the image to greyscale white or black. Any pixel greather-than-or-equal-to the threshold (0..255) will be white. All others will be black.
* `threshold`, if present, is a Number, representing the level above which pixels will be forced to white.
* `options`, an options object that may contain a boolean `grayscale` or `greyscale`. When `grayscale` is `true`, `threshold` returns a black and white image, and when `false` a color image with each channel thresholded independently. The default is `grayscale: true` when omitted.
#### gamma([gamma])
Apply a gamma correction by reducing the encoding (darken) pre-resize at a factor of `1/gamma` then increasing the encoding (brighten) post-resize at a factor of `gamma`.