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40 changes: 20 additions & 20 deletions README.md
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Expand Up @@ -38,10 +38,10 @@ A lightweight image comparison tool
* [License](#license)


##Image Comparison and Result
## Image Comparison and Result
![Composition](https://raw.githubusercontent.com/yahoo/blink-diff/master/images/composition.png)

##Installation
## Installation

Install this module with the following command:
```shell
Expand All @@ -57,13 +57,13 @@ Add the module to your ```package.json``` dev-dependencies:
npm install --save-dev blink-diff
```

##Usage
## Usage

The package can be used in two different ways:
* per command line
* through an object

###Command-Line usage
### Command-Line usage

The command-line tool can be found in the ```bin``` directory. You can run the application with

Expand Down Expand Up @@ -98,7 +98,7 @@ The command-line tool exposes a couple of flags and parameters for the compariso
```


###Object usage
### Object usage

The package can also be used directly in code, without going through the command-line.

Expand Down Expand Up @@ -207,13 +207,13 @@ var firstImage = PNGImage.readImage('path/to/first/image', function (err) {
});
```

####Cropping
#### Cropping
Images can be cropped before they are compared by using the ```cropImageA``` or ```cropImageB``` parameters. Single values can be left off, and the system will calculate the correct dimensions. However, ```x```/```y``` coordinates have priority over ```width```/```height``` as the position are usually more important than the dimensions - image will also be clipped by the system when needed.

####Perceptual Comparison
#### Perceptual Comparison
The perceptual comparison mode considers the perception of colors in the human brain. It transforms all the colors into a human perception color-space, which is quite different to the typical physical bound RGB color-space. There, in the perceptual color-space, the distance between colors is according to the human perception and should therefore closer resemble the differences a human would perceive seeing the images.

####Logging
#### Logging

By default, the logger doesn't log events anywhere, but you can change this behavior by overwriting ```blinkDiff.log```:

Expand All @@ -229,12 +229,12 @@ blinkDiff.log = function (text) {
...
```

####Block-Out
#### Block-Out
Sometimes, it is necessary to block-out some specific areas in an image that should be ignored for comparisons. For example, this can be IDs or even time-labels that change with the time. Adding block-outs to images may decrease false positives and therefore stabilizes these comparisons.

The color of the block-outs can be selected by the API parameters. However, the block-out areas will not be visible by default - they are hidden even though they are used. To make them visible, turn the debug-mode on.

##Examples
## Examples

There are some examples in the ```examples``` folder, in which I used screenshots of YDN to check for visual regressions (and made some manual modifications to the dom to make differences appear ;-)).
You can find examples for:
Expand All @@ -248,23 +248,23 @@ You can find examples for:
All screenshots were compared to ```YDN.png```, a previously approved screenshot without a regression.
Each of the regressions has the screenshot and the output result, highlighting the differences.

##API-Documentation
## API-Documentation

Generate the documentation with following command:
```shell
npm run docs
```
The documentation will be generated in the ```docs``` folder of the module root.

##Tests
## Tests

Run the tests with the following command:
```shell
npm run test
```
The code-coverage will be written to the ```coverage``` folder in the module root.

##Project Focus
## Project Focus
There are three types of image comparisons:
* Pixel-by-pixel - Used to compare low-frequency images like screenshots from web-sites, making sure that small styling differences trigger
* Perceptual - Used to compare image creation applications, for example rendering engines and photo manipulation applications that are taking the human perception into account, ignoring differences a human probably would not see
Expand All @@ -275,31 +275,31 @@ A perceptual comparison would not trigger small differences, possibly missing pr
Pixel-by-pixel comparisons have the reputation of triggering too often, adding manual labor, checking images by hand. Blink-Diff was created to keep this in mind and was optimized to reduce false-positives by taking sub-pixeling and anti-aliasing into account. Additional features like thresholds and the pythagorean distance calculation in the four dimensional color-space makes sure that this won't happen too often. Additionally, filters can be applied to the images, for example to compare luminosity of pixels and not the saturation thereof.
Blink-Diff also supports partially the perceptual comparison that can be turned on when supplying ```perceptual=true```. Then, the colors will be compared in accordance with the human perception and not according to the physical world. High-frequency filters, however, are not yet supported.

##Project Naming
## Project Naming
The name comes from the [Blink comparator](http://en.wikipedia.org/wiki/Blink_comparator) that was used in Astronomy to recognize differences in multiple photos, taking a picture of the same area in the sky over consecutive days, months, or years. Most notably, it was used to discover Pluto.

##Contributions
## Contributions
Feel free to create an issue or create a pull-request if you have an idea on how to improve blink-diff. We are pretty relaxed on the contribution rules; add tests for your pull-requests when possible, but it is also ok if there are none - we'll add them for you. We are trying to improve blink-diff as much as possible, and this can only be done by contributions from the community.

Also, even if you simply gave us an idea for a feature and did not actually write the code, we will still add you as the Contributor down below since it probably wouldn't be there without you. So, keep them coming!

##Contributors
## Contributors
* [sarbbottam](https://github.com/sarbbottam)
* [koola](https://github.com/koola)
* [jeffposnick](https://github.com/jeffposnick)
* [a-nwhitmont](https://github.com/a-nwhitmont)
* [azu](https://github.com/azu)
* [bradex](https://github.com/bradex)

##Third-party libraries
## Third-party libraries

The following third-party libraries are used by this module:

###Dependencies
### Dependencies
* promise: https://github.com/then/promise
* pngjs-image: https://github.com/yahoo/pngjs-image

###Dev-Dependencies
### Dev-Dependencies
* chai: http://chaijs.com
* coveralls: https://github.com/cainus/node-coveralls
* codeclimate-test-reporter: https://github.com/codeclimate/javascript-test-reporter
Expand All @@ -309,7 +309,7 @@ The following third-party libraries are used by this module:
* sinon-chai: https://github.com/domenic/sinon-chai
* yuidocjs: https://github.com/yui/yuidoc

##License
## License

The MIT License

Expand Down