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Avoid (un)premultiplication for overlay image without alpha channel

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Add 'premultiplied' boolean attribute to output info, helps test
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Lovell Fuller
2017-03-25 16:52:09 +00:00
parent 301bfbd271
commit 1169afbe90
11 changed files with 109 additions and 104 deletions
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2
docs/api-composite.md
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@@ -11,6 +11,8 @@ Overlay (composite) an image over the processed (resized, extracted etc.) image.
The overlay image must be the same size or smaller than the processed image.
If both `top` and `left` options are provided, they take precedence over `gravity`.
If the overlay image contains an alpha channel then composition with premultiplication will occur.
**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.

6
docs/api-output.md
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@@ -27,7 +27,8 @@ A Promises/A+ promise is returned when `callback` is not provided.
- `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)`.
`info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
`info` contains the output image `format`, `size` (bytes), `width`, `height`,
`channels` and `premultiplied` (indicating if premultiplication was used).
- Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** Invalid parameters
@@ -44,7 +45,8 @@ By default, the format will match the input image, except GIF and SVG input whic
- `err` is an error, if any.
- `data` is the output image data.
- `info` contains the output image `format`, `size` (bytes), `width`, `height` and `channels`.
- `info` contains the output image `format`, `size` (bytes), `width`, `height`,
`channels` and `premultiplied` (indicating if premultiplication was used).
A Promise is returned when `callback` is not provided.
**Parameters**

4
docs/changelog.md
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@@ -6,6 +6,10 @@ Requires libvips v8.5.2.
#### v0.18.0 - TBD
* Avoid costly (un)premultiply when using overlayWith without alpha channel.
[#573](https://github.com/lovell/sharp/issues/573)
[@strarsis](https://github.com/strarsis)
* Expose warnings from libvips via NODE_DEBUG=sharp environment variable.
[#607](https://github.com/lovell/sharp/issues/607)
[@puzrin](https://github.com/puzrin)