diff --git a/docs/api-colour.md b/docs/api-colour.md
index 02948179..8598227b 100644
--- a/docs/api-colour.md
+++ b/docs/api-colour.md
@@ -29,7 +29,7 @@ An alpha channel may be present, and will be unchanged by the operation.
 
 **Parameters**
 
--   `greyscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `greyscale` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -39,7 +39,7 @@ Alternative spelling of `greyscale`.
 
 **Parameters**
 
--   `grayscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `grayscale` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -50,7 +50,7 @@ By default output image will be web-friendly sRGB, with additional channels inte
 
 **Parameters**
 
--   `colourspace` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
+-   `colourspace` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** output colourspace e.g. `srgb`, `rgb`, `cmyk`, `lab`, `b-w` [...](https://github.com/jcupitt/libvips/blob/master/libvips/iofuncs/enumtypes.c#L568)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -63,7 +63,7 @@ Alternative spelling of `toColourspace`.
 
 **Parameters**
 
--   `colorspace` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** output colorspace.
+-   `colorspace` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** output colorspace.
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
diff --git a/docs/api-composite.md b/docs/api-composite.md
index e4481273..68eee27a 100644
--- a/docs/api-composite.md
+++ b/docs/api-composite.md
@@ -10,16 +10,16 @@ If both `top` and `left` options are provided, they take precedence over `gravit
 **Parameters**
 
 -   `overlay` **([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))** Buffer containing image data or String containing the path to an image file.
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `options.gravity` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** gravity at which to place the overlay. (optional, default `'centre'`)
-    -   `options.top` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the pixel offset from the top edge.
-    -   `options.left` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the pixel offset from the left edge.
-    -   `options.tile` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
-    -   `options.cutout` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** set to true to apply only the alpha channel of the overlay image to the input image, giving the appearance of one image being cut out of another. (optional, default `false`)
-    -   `options.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes overlay when using raw pixel data.
-        -   `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `options.gravity` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** gravity at which to place the overlay. (optional, default `'centre'`)
+    -   `options.top` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the pixel offset from the top edge.
+    -   `options.left` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the pixel offset from the left edge.
+    -   `options.tile` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** set to true to repeat the overlay image across the entire image with the given `gravity`. (optional, default `false`)
+    -   `options.cutout` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** set to true to apply only the alpha channel of the overlay image to the input image, giving the appearance of one image being cut out of another. (optional, default `false`)
+    -   `options.raw` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** describes overlay when using raw pixel data.
+        -   `options.raw.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.channels` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
 
 **Examples**
 
diff --git a/docs/api-constructor.md b/docs/api-constructor.md
index 6c959c2f..9c6371fb 100644
--- a/docs/api-constructor.md
+++ b/docs/api-constructor.md
@@ -4,16 +4,16 @@
 
 **Parameters**
 
--   `input` **\[([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))]** if present, can be
+-   `input` **([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))?** if present, can be
      a Buffer containing JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data, or
      a String containing the path to an JPEG, PNG, WebP, GIF, SVG or TIFF image file.
      JPEG, PNG, WebP, GIF, SVG, TIFF or raw pixel image data can be streamed into the object when null or undefined.
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** if present, is an Object with optional attributes.
-    -   `options.density` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** integral number representing the DPI for vector images. (optional, default `72`)
-    -   `options.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes raw pixel image data. See `raw()` for pixel ordering.
-        -   `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** if present, is an Object with optional attributes.
+    -   `options.density` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** integral number representing the DPI for vector images. (optional, default `72`)
+    -   `options.raw` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** describes raw pixel image data. See `raw()` for pixel ordering.
+        -   `options.raw.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.channels` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
 
 **Examples**
 
diff --git a/docs/api-input.md b/docs/api-input.md
index 28207842..7a9918f4 100644
--- a/docs/api-input.md
+++ b/docs/api-input.md
@@ -38,7 +38,7 @@ A Promises/A+ promise is returned when `callback` is not provided.
 
 **Parameters**
 
--   `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]** called with the arguments `(err, metadata)`
+-   `callback` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)?** called with the arguments `(err, metadata)`
 
 **Examples**
 
@@ -81,6 +81,6 @@ This will reduce memory usage and can improve performance on some systems.
 
 **Parameters**
 
--   `sequentialRead` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `sequentialRead` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
diff --git a/docs/api-operation.md b/docs/api-operation.md
index 4c5dbfc0..3ef71bef 100644
--- a/docs/api-operation.md
+++ b/docs/api-operation.md
@@ -15,7 +15,7 @@ for example `rotate(x).extract(y)` will produce a different result to `extract(y
 
 **Parameters**
 
--   `angle` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 0, 90, 180 or 270. (optional, default `auto`)
+-   `angle` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 0, 90, 180 or 270. (optional, default `auto`)
 
 **Examples**
 
@@ -82,7 +82,7 @@ The use of `flip` implies the removal of the EXIF `Orientation` tag, if any.
 
 **Parameters**
 
--   `flip` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `flip` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -93,7 +93,7 @@ The use of `flop` implies the removal of the EXIF `Orientation` tag, if any.
 
 **Parameters**
 
--   `flop` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `flop` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -106,9 +106,9 @@ Separate control over the level of sharpening in "flat" and "jagged" areas is av
 
 **Parameters**
 
--   `sigma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
--   `flat` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the level of sharpening to apply to "flat" areas. (optional, default `1.0`)
--   `jagged` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the level of sharpening to apply to "jagged" areas. (optional, default `2.0`)
+-   `sigma` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
+-   `flat` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the level of sharpening to apply to "flat" areas. (optional, default `1.0`)
+-   `jagged` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the level of sharpening to apply to "jagged" areas. (optional, default `2.0`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -123,7 +123,7 @@ When a `sigma` is provided, performs a slower, more accurate Gaussian blur.
 
 **Parameters**
 
--   `sigma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
+-   `sigma` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** a value between 0.3 and 1000 representing the sigma of the Gaussian mask, where `sigma = 1 + radius / 2`.
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -138,10 +138,10 @@ This operation will always occur after resizing and extraction, if any.
 **Parameters**
 
 -   `extend` **([Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number) \| [Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object))** single pixel count to add to all edges or an Object with per-edge counts
-    -   `extend.top` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-    -   `extend.left` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-    -   `extend.bottom` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-    -   `extend.right` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
+    -   `extend.top` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+    -   `extend.left` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+    -   `extend.bottom` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+    -   `extend.right` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
 
 **Examples**
 
@@ -165,7 +165,7 @@ Merge alpha transparency channel, if any, with `background`.
 
 **Parameters**
 
--   `flatten` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `flatten` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -175,7 +175,7 @@ Trim "boring" pixels from all edges that contain values within a percentage simi
 
 **Parameters**
 
--   `tolerance` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1 and 99 representing the percentage similarity. (optional, default `10`)
+-   `tolerance` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** value between 1 and 99 representing the percentage similarity. (optional, default `10`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -192,7 +192,7 @@ when applying a gamma correction.
 
 **Parameters**
 
--   `gamma` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1.0 and 3.0. (optional, default `2.2`)
+-   `gamma` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** value between 1.0 and 3.0. (optional, default `2.2`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -205,7 +205,7 @@ Produce the "negative" of the image.
 
 **Parameters**
 
--   `negate` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `negate` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -215,7 +215,7 @@ Enhance output image contrast by stretching its luminance to cover the full dyna
 
 **Parameters**
 
--   `normalise` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `normalise` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -225,7 +225,7 @@ Alternative spelling of normalise.
 
 **Parameters**
 
--   `normalize` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `normalize` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
 
@@ -239,8 +239,8 @@ Convolve the image with the specified kernel.
     -   `kernel.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** width of the kernel in pixels.
     -   `kernel.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** width of the kernel in pixels.
     -   `kernel.kernel` **[Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array)<[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)>** Array of length `width*height` containing the kernel values.
-    -   `kernel.scale` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the scale of the kernel in pixels. (optional, default `sum`)
-    -   `kernel.offset` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** the offset of the kernel in pixels. (optional, default `0`)
+    -   `kernel.scale` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the scale of the kernel in pixels. (optional, default `sum`)
+    -   `kernel.offset` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** the offset of the kernel in pixels. (optional, default `0`)
 
 **Examples**
 
@@ -268,10 +268,10 @@ Any pixel value greather than or equal to the threshold value will be set to 255
 
 **Parameters**
 
--   `threshold` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** a value in the range 0-255 representing the level at which the threshold will be applied. (optional, default `128`)
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `options.greyscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** convert to single channel greyscale. (optional, default `true`)
-    -   `options.grayscale` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** alternative spelling for greyscale. (optional, default `true`)
+-   `threshold` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** a value in the range 0-255 representing the level at which the threshold will be applied. (optional, default `128`)
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `options.greyscale` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** convert to single channel greyscale. (optional, default `true`)
+    -   `options.grayscale` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** alternative spelling for greyscale. (optional, default `true`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -289,11 +289,11 @@ the selected bitwise boolean `operation` between the corresponding pixels of the
 
 -   `operand` **([Buffer](https://nodejs.org/api/buffer.html) \| [String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String))** Buffer containing image data or String containing the path to an image file.
 -   `operator` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** one of `and`, `or` or `eor` to perform that bitwise operation, like the C logic operators `&`, `|` and `^` respectively.
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `options.raw` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** describes operand when using raw pixel data.
-        -   `options.raw.width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
-        -   `options.raw.channels` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `options.raw` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** describes operand when using raw pixel data.
+        -   `options.raw.width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
+        -   `options.raw.channels` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
diff --git a/docs/api-output.md b/docs/api-output.md
index 353e2dc1..fe8a8fe9 100644
--- a/docs/api-output.md
+++ b/docs/api-output.md
@@ -13,7 +13,7 @@ A Promises/A+ promise is returned when `callback` is not provided.
 **Parameters**
 
 -   `fileOut` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)** the path to write the image data to.
--   `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]** called on completion with two arguments `(err, info)`.
+-   `callback` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)?** called on completion with two arguments `(err, info)`.
     `info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
 
 
@@ -34,7 +34,7 @@ By default, the format will match the input image. JPEG, PNG, WebP, and RAW are
 
 **Parameters**
 
--   `callback` **\[[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)]** 
+-   `callback` **[Function](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function)?** 
 
 Returns **[Promise](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise)<[Buffer](https://nodejs.org/api/buffer.html)>** when no callback is provided
 
@@ -46,8 +46,8 @@ This will also convert to and add a web-friendly sRGB ICC profile.
 
 **Parameters**
 
--   `withMetadata` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `withMetadata.orientation` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** value between 1 and 8, used to update the EXIF `Orientation` tag.
+-   `withMetadata` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `withMetadata.orientation` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** value between 1 and 8, used to update the EXIF `Orientation` tag.
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -60,15 +60,15 @@ Use these JPEG options for output image.
 
 **Parameters**
 
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
-    -   `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
-    -   `options.progressive` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use progressive (interlace) scan (optional, default `false`)
-    -   `options.chromaSubsampling` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** set to '4:4:4' to prevent chroma subsampling when quality <= 90 (optional, default `'4:2:0'`)
-    -   `options.trellisQuantisation` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** apply trellis quantisation, requires mozjpeg (optional, default `false`)
-    -   `options.overshootDeringing` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** apply overshoot deringing, requires mozjpeg (optional, default `false`)
-    -   `options.optimiseScans` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** optimise progressive scans, forces progressive, requires mozjpeg (optional, default `false`)
-    -   `options.optimizeScans` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** alternative spelling of optimiseScans (optional, default `false`)
-    -   `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force JPEG output, otherwise attempt to use input format (optional, default `true`)
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** output options
+    -   `options.quality` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** quality, integer 1-100 (optional, default `80`)
+    -   `options.progressive` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** use progressive (interlace) scan (optional, default `false`)
+    -   `options.chromaSubsampling` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** set to '4:4:4' to prevent chroma subsampling when quality <= 90 (optional, default `'4:2:0'`)
+    -   `options.trellisQuantisation` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** apply trellis quantisation, requires mozjpeg (optional, default `false`)
+    -   `options.overshootDeringing` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** apply overshoot deringing, requires mozjpeg (optional, default `false`)
+    -   `options.optimiseScans` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** optimise progressive scans, forces progressive, requires mozjpeg (optional, default `false`)
+    -   `options.optimizeScans` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** alternative spelling of optimiseScans (optional, default `false`)
+    -   `options.force` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** force JPEG output, otherwise attempt to use input format (optional, default `true`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
@@ -81,11 +81,11 @@ Use these PNG options for output image.
 
 **Parameters**
 
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `options.progressive` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use progressive (interlace) scan (optional, default `false`)
-    -   `options.compressionLevel` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** zlib compression level (optional, default `6`)
-    -   `options.adaptiveFiltering` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use adaptive row filtering (optional, default `true`)
-    -   `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force PNG output, otherwise attempt to use input format (optional, default `true`)
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `options.progressive` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** use progressive (interlace) scan (optional, default `false`)
+    -   `options.compressionLevel` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** zlib compression level (optional, default `6`)
+    -   `options.adaptiveFiltering` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** use adaptive row filtering (optional, default `true`)
+    -   `options.force` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** force PNG output, otherwise attempt to use input format (optional, default `true`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
@@ -98,9 +98,9 @@ Use these WebP options for output image.
 
 **Parameters**
 
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
-    -   `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
-    -   `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force WebP output, otherwise attempt to use input format (optional, default `true`)
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** output options
+    -   `options.quality` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** quality, integer 1-100 (optional, default `80`)
+    -   `options.force` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** force WebP output, otherwise attempt to use input format (optional, default `true`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
@@ -113,9 +113,9 @@ Use these TIFF options for output image.
 
 **Parameters**
 
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** output options
-    -   `options.quality` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** quality, integer 1-100 (optional, default `80`)
-    -   `options.force` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** force TIFF output, otherwise attempt to use input format (optional, default `true`)
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** output options
+    -   `options.quality` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** quality, integer 1-100 (optional, default `80`)
+    -   `options.force` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** force TIFF output, otherwise attempt to use input format (optional, default `true`)
 
 
 -   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid options
@@ -150,11 +150,11 @@ Use a `.zip` or `.szi` file extension with `toFile` to write to a compressed arc
 
 **Parameters**
 
--   `tile` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `tile.size` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** tile size in pixels, a value between 1 and 8192. (optional, default `256`)
-    -   `tile.overlap` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** tile overlap in pixels, a value between 0 and 8192. (optional, default `0`)
-    -   `tile.container` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** tile container, with value `fs` (filesystem) or `zip` (compressed file). (optional, default `'fs'`)
-    -   `tile.layout` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** filesystem layout, possible values are `dz`, `zoomify` or `google`. (optional, default `'dz'`)
+-   `tile` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `tile.size` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** tile size in pixels, a value between 1 and 8192. (optional, default `256`)
+    -   `tile.overlap` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** tile overlap in pixels, a value between 0 and 8192. (optional, default `0`)
+    -   `tile.container` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** tile container, with value `fs` (filesystem) or `zip` (compressed file). (optional, default `'fs'`)
+    -   `tile.layout` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** filesystem layout, possible values are `dz`, `zoomify` or `google`. (optional, default `'dz'`)
 
 **Examples**
 
diff --git a/docs/api-resize.md b/docs/api-resize.md
index 8b54ccf4..b6382402 100644
--- a/docs/api-resize.md
+++ b/docs/api-resize.md
@@ -22,13 +22,13 @@ Possible enlargement interpolators are:
 
 **Parameters**
 
--   `width` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** pixels wide the resultant image should be, between 1 and 16383 (0x3FFF). Use `null` or `undefined` to auto-scale the width to match the height.
--   `height` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** pixels high the resultant image should be, between 1 and 16383. Use `null` or `undefined` to auto-scale the height to match the width.
--   `options` **\[[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)]** 
-    -   `options.kernel` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** the kernel to use for image reduction. (optional, default `'lanczos3'`)
-    -   `options.interpolator` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** the interpolator to use for image enlargement. (optional, default `'bicubic'`)
-    -   `options.centreSampling` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** use \*magick centre sampling convention instead of corner sampling. (optional, default `false`)
-    -   `options.centerSampling` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]** alternative spelling of centreSampling. (optional, default `false`)
+-   `width` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** pixels wide the resultant image should be, between 1 and 16383 (0x3FFF). Use `null` or `undefined` to auto-scale the width to match the height.
+-   `height` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** pixels high the resultant image should be, between 1 and 16383. Use `null` or `undefined` to auto-scale the height to match the width.
+-   `options` **[Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object)?** 
+    -   `options.kernel` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** the kernel to use for image reduction. (optional, default `'lanczos3'`)
+    -   `options.interpolator` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** the interpolator to use for image enlargement. (optional, default `'bicubic'`)
+    -   `options.centreSampling` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** use \*magick centre sampling convention instead of corner sampling. (optional, default `false`)
+    -   `options.centerSampling` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?** alternative spelling of centreSampling. (optional, default `false`)
 
 **Examples**
 
@@ -67,7 +67,7 @@ then repeatedly ranks edge regions, discarding the edge with the lowest score ba
 
 **Parameters**
 
--   `crop` **\[[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** A member of `sharp.gravity` to crop to an edge/corner or `sharp.strategy` to crop dynamically. (optional, default `'centre'`)
+-   `crop` **[String](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)?** A member of `sharp.gravity` to crop to an edge/corner or `sharp.strategy` to crop dynamically. (optional, default `'centre'`)
 
 **Examples**
 
@@ -161,6 +161,6 @@ This is equivalent to GraphicsMagick's `>` geometry option:
 
 **Parameters**
 
--   `withoutEnlargement` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `true`)
+-   `withoutEnlargement` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `true`)
 
 Returns **Sharp** 
diff --git a/docs/api-utility.md b/docs/api-utility.md
index 20d78618..1871aee4 100644
--- a/docs/api-utility.md
+++ b/docs/api-utility.md
@@ -10,9 +10,9 @@ useful for determining how much working memory is required for a particular task
 **Parameters**
 
 -   `options` **([Object](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object) \| [Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean))** Object with the following attributes, or Boolean where true uses default cache settings and false removes all caching.
-    -   `options.memory` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum memory in MB to use for this cache (optional, default `50`)
-    -   `options.files` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum number of files to hold open (optional, default `20`)
-    -   `options.items` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** is the maximum number of operations to cache (optional, default `100`)
+    -   `options.memory` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** is the maximum memory in MB to use for this cache (optional, default `50`)
+    -   `options.files` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** is the maximum number of files to hold open (optional, default `20`)
+    -   `options.items` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** is the maximum number of operations to cache (optional, default `100`)
 
 **Examples**
 
@@ -42,7 +42,7 @@ This method always returns the current concurrency.
 
 **Parameters**
 
--   `concurrency` **\[[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** 
+-   `concurrency` **[Number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)?** 
 
 **Examples**
 
@@ -82,7 +82,7 @@ Versions of liborc prior to 0.4.25 are known to segfault under heavy load.
 
 **Parameters**
 
--   `simd` **\[[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)]**  (optional, default `false`)
+-   `simd` **[Boolean](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean)?**  (optional, default `false`)
 
 **Examples**
 
diff --git a/package.json b/package.json
index 57161d82..ba4871ca 100644
--- a/package.json
+++ b/package.json
@@ -68,15 +68,15 @@
     "tar": "^2.2.1"
   },
   "devDependencies": {
-    "async": "^2.1.2",
-    "bufferutil": "^1.2.1",
+    "async": "^2.1.4",
+    "bufferutil": "^1.3.0",
     "cross-env": "^3.1.3",
-    "documentation": "^4.0.0-beta13",
+    "documentation": "^4.0.0-beta15",
     "exif-reader": "^1.0.1",
     "icc": "^0.0.2",
-    "mocha": "^3.1.2",
+    "mocha": "^3.2.0",
     "node-cpplint": "^0.4.0",
-    "nyc": "^9.0.1",
+    "nyc": "^10.0.0",
     "rimraf": "^2.5.4",
     "semistandard": "^9.1.0",
     "unzip": "^0.1.11"