FisheyeGl
====

A library for correcting fisheye, or barrel distortion, on images in the browser in JavaScript with WebGL.

Adapted from [fisheye-correction-webgl](https://github.com/bluemir/fisheye-correction-webgl) by @bluemir.

## Usage

In the [live demo](https://jywarren.github.io/fisheyegl/example/), you can try it out -- use the default image or drag a new one in, and use the sliders to adjust the distortion.

Right click the image to save. Drag a new image in to use the same settings for multiple images.

## Presets

You can now use the example page to generate preset URLs, since the settings are now stored in the URL (only in the demo):

* Mobius Action Cam (default lens): https://jywarren.github.io/fisheyegl/example/#a=1.048&b=1.059&Fx=0.09&Fy=0.22&scale=1.087&x=1&y=1
* [GoPro alternatives](https://publiclab.org/questions/warren/05-20-2017/cheap-lightweight-gopro-alternatives-for-aerial-mapping) (many almost identical): https://jywarren.github.io/fisheyegl/example/#a=1&b=1&Fx=0.16&Fy=0.16&scale=1.087&x=1&y=1

## Lens models

If you can manually correct a particular lens or camera, please [file an issue](https://github.com/jywarren/fisheyegl/issues) or email jeff@publiclab.org to get a preset made; we can save up some presets and add a feature for quick correction of known cameras. Please include the `a`, `b`, `Fx`, `Fy`, and `fov` parameters and the make/model of your camera with a before/after image pair, so we can add them to a presets listing.

## Example before/after images:

Before correcting lens (barrel) distortion:

![grid.png](https://raw.githubusercontent.com/jywarren/fisheyegl/master/example/images/grid.png)

After:

![grid-fixed.png](https://raw.githubusercontent.com/jywarren/fisheyegl/master/example/images/grid-fixed.png)

## Using it in your code

See `main.js` in the examples folder for a working implementation, but the basics are:

```js
var distorter = FisheyeGl({
  image: 'path/to/image.jpg',
  selector: '#canvas', // a canvas element to work with
  lens: {
    a: 1,    // 0 to 4;  default 1
    b: 1,    // 0 to 4;  default 1
    Fx: 0.0, // 0 to 4;  default 0.0
    Fy: 0.0, // 0 to 4;  default 0.0
   scale: 1.5 // 0 to 20; default 1.5
  },
  fov: {
    x: 1, // 0 to 2; default 1
    y: 1  // 0 to 2; default 1
  },
  fragmentSrc: "path/to/fragment.glfs", // optional, defaults to an inbuilt fragment shader 
  vertexSrc:   "path/to/vertex.glvs" // optional, defaults to an inbuilt vertex shader
});

distorter.getImage(); // <= returns a native JavaScript Image object based on the DOM element
distorter.getImage('image/png'); // <= format can be specified

distorter.setImage('path/to/image.jpg'); // <= load a new image with the same distortion settings
```

You do not need to provide links to shader files, but you may, if you wish to use a custom shader.


## Resources

Lots of good info here: http://wiki.panotools.org/Lens_correction_model#Lens_distortion_a.2C_b_.26_c_parameters