sharp/CONTRIBUTING.md
Lovell Fuller bdac84059d Update perf results for forthcoming v0.13.0
Install runtime rather than dev pkgs on Alpine Linux
2016-02-12 19:33:21 +00:00

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# Contributing to sharp
Hello, thank you for your interest in helping!
## Submit a new bug report
Please create a [new issue](https://github.com/lovell/sharp/issues/new) containing the steps to reproduce the problem.
If you're having installation problems, please include the output of running `npm install --verbose sharp`.
New bugs are assigned a `triage` label whilst under investigation.
## Submit a new feature request
If a [similar request](https://github.com/lovell/sharp/labels/enhancement) exists, it's probably fastest to add a comment to it about your requirement.
Implementation is usually straightforward if _libvips_ [already supports](http://www.vips.ecs.soton.ac.uk/supported/current/doc/html/libvips/ch03.html) the feature you need.
## Submit a Pull Request to fix a bug
Thank you! To prevent the problem occurring again, please add unit tests that would have failed.
Please select the `master` branch as the destination for your Pull Request so your fix can be included in the next minor release.
Please squash your changes into a single commit using a command like `git rebase -i upstream/master`.
To test C++ changes, you can compile the module using `npm install` and then run the tests using `npm test`.
## Submit a Pull Request with a new feature
Please add JavaScript [unit tests](https://github.com/lovell/sharp/tree/master/test/unit) to cover your new feature.
A test coverage report for the JavaScript code is generated in the `coverage/lcov-report` directory.
Where possible, the functional tests use gradient-based perceptual hashes
based on [dHash](http://www.hackerfactor.com/blog/index.php?/archives/529-Kind-of-Like-That.html)
to compare expected vs actual images.
You deserve to add your details to the [list of contributors](https://github.com/lovell/sharp/blob/master/package.json#L5).
Any change that modifies the existing public API should be added to the relevant work-in-progress branch for inclusion in the next major release.
| Release | WIP branch |
| ------: | :--------- |
| v0.14.0 | needle |
| v0.15.0 | outfit |
| v0.16.0 | pencil |
Please squash your changes into a single commit using a command like `git rebase -i upstream/<wip-branch>`.
### Add a new public method
The API tries to be as fluent as possible. Image processing concepts follow the naming conventions from _libvips_ and, to a lesser extent, _ImageMagick_.
Most methods have optional parameters and assume sensible defaults. Methods with mandatory parameters often have names like `doSomethingWith(X)`.
Please ensure backwards compatibility where possible. Methods to modify previously default behaviour often have names like `withoutOptionY()` or `withExtraZ()`.
Feel free to create a [new issue](https://github.com/lovell/sharp/issues/new) to gather feedback on a potential API change.
### Remove an existing public method
A method to be removed should be deprecated in the next major version then removed in the following major version.
By way of example, the [bilinearInterpolation method](https://github.com/lovell/sharp/blob/v0.6.0/index.js#L155) present in v0.5.0 was deprecated in v0.6.0 and removed in v0.7.0.
## Run the tests
### Functional tests and static code analysis
```sh
npm test
```
### Memory leak tests
Requires [Valgrind](http://valgrind.org/).
```sh
npm run test-leak
```
### Packaging tests
Tests the installation on a number of Linux-based operating systems.
Requires docker.
```sh
npm run test-packaging
```
## Finally
Please feel free to ask any questions via a [new issue](https://github.com/lovell/sharp/issues/new) or contact me by [e-mail](https://github.com/lovell/sharp/blob/master/package.json#L4).