# image-diffr

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A simple tool for comparing the similarity between two images. Works on PNGs and JPGs, both from the command line and as a require()able module. Responds with a weighted percentage of the differences between the images based on a threshold value, and/or generates a new image highlighting the differences between the two inputs.

![Alt text](./docs/cli-default.png?raw=true "CLI Output")

#### Inputs & Diff Result

![Alt text](./docs/glasses1.png?raw=true "Diff Images")
![Alt text](./docs/glasses2.png?raw=true "Diff Images")
![Alt text](./docs/glassesDiff.png?raw=true "Diff Images")

**Full credit for the underlying image diff'ing/analysis goes to [Jimp](https://www.npmjs.com/package/jimp) and related authors. This is effectively a wrapper (CLI & node module) for easy use.**

---

## Installation

Easy command line use:

    npm install -g image-diffr

or to use as a module in another project:

    npm install --save image-diffr

---

## CLI Usage

    image-diffr ./path/to/1.png ./path/to/2.png

### Options

  - Threshold `-t [value], --threshold [value]`

    How stringent should the comparison be (0 to 1: 0 being perfect match, 1 being pretty damn lack·a·dai·si·cal).

        image-diffr ./path/to/1.png ./path/to/2.png -t 0.25
    
  - Output `-o [path], --output [path]`

    Output an image highlighting the differences between the two input images. The file extension you specify in the name of the output file name (.jpg below) should match the input file types.

        image-diffr ./path/to/1.png ./path/to/2.png -o /tmp/diff.jpg

  - Output Only If Different `-d [true|false], --differentonly [true|false]`

    If using the `output` option to render a diff of the two images to disk, should it only output *if there is a difference*?
  
  - Quit `-q, --quiet`

    By default, image-diffr will show a few stats (see image above) when run. To silence that business, pass `-q` or `--quiet` and it'll become this:

    ![Alt text](./docs/cli-quiet.png?raw=true "Quit CLI output")
  
  - Help

    Invoke without any arguments

        $: image-diffr

        Options:

        -h, --help                           output usage information
        -V, --version                        output the version number
        -t, --threshold [threshold]          Diff comparison threshold (0-1, eg. 0.25)
        -o, --output [output]                Image diff output (absolute path, eg. /tmp/diff-image.jpg)
        -d, --differentonly [differentonly]  Only write output image (-o/--output flags) if different
        -q, --quiet [quiet]                  Skip detailed output and show diff percentage only

---

## Module usage

When `require()`ing as a node_module, no output will be logged to stdout. There is a single method with a 3 parameter arity: `.exec(imagePath1 string, imagePath2 string, options {})`.

The `.exec()` method returns a Promise, which resolves with a _Jimp_ image instance. If an error occurs, be sure to `catch` it as shown below.

    const imageDiffr = require('image-diffr');
    const image1Path = '/path/from/root/image1.jpg';
    const image2Path = '/path/from/root/image2.jpg';
    imageDiffr
        .exec(image1Path, image2Path, {
            threshold: 0.3,
            output: '/tmp/diffedresult.jpg'
        })
        .then(diff => {
            console.log(diff.percent);
            console.log(diff.image);
        })
        .catch(err => {
            // handle error
        });

### Options

  - Threshold `{threshold: 0.1}` [optional | default: 0]

    How stringent should the comparison be (0 to 1: 0 being perfect match, 1 being pretty damn lack·a·dai·si·cal).
    
  - Output `{output: '/path/somewhere.jpg'}` [optional | default: null]

    Output an image highlighting the differences between the two input images. The file extension you specify in the name of the output file name (.jpg below) should match the input file types.

  - Output Only If Different `{outputOnlyIfDifferent: true}` [optional | default: true]

    If using the `output` option to render a diff of the two images to disk, should it only output *if there is a difference*?

---

## Running tests

    npm test


## License

(The MIT License)

Copyright (c) 2017 Fluid, Inc, Jon Hartman <jhartman@fluid.com>

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
'Software'), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.