improved README

Author: aquatiko

Images/input.png

@@ -7,9 +7,69 @@ Implementation in [Julia](https://julialang.org/) of the
 [`reproject`](https://github.com/astropy/reproject) package by Thomas
 Robitaille, part of the Astropy project.
 
+This package can be used to reproject Astronomical Images from one world coordinate to another. By reproject we mean re-gridding of images using interpolation (i.e changing the pixel resolution, orientation, coordinate system).
+
+Installation
+-------
+
+`Reproject.jl` is avilable for Julia 1.0 and later versions and can be installed with [Julia built-in package manager](https://docs.julialang.org/en/v1/stdlib/Pkg/).
+`julia> Pkg.add("Reproject")`
+
+Usage
+-------
+
+After installing the package, you can start using it with
+
+```
+julia> using Reproject
+julia> result = reproject(input_data, output_projection)
+```
+
+This returns a tuple of reprojected Image and footprint. 
+
+
+Reprojecting Images
+-------
+
+To reproject Astronomical Images, primary requirements are Image data (2D Matrix), world cordinate frame of input Image and required output frame in which it needs to be reprojected. 
+
+The Image data and input frame is given together as an [ImageHDU](http://juliaastro.github.io/FITSIO.jl/latest/index.html) or [FITS](https://github.com/JuliaAstro/FITSIO.jl) file or name of the FITS file in `input_data`. A keyword argument `hdu_in` can be given while using FITS or FITS file name to specify specific HDU in FITS file.
+
+The `output_projection` is the output world coordinate frame and needs to be a a [WCSTransform](https://github.com/JuliaAstro/WCS.jl) or an [ImageHDU](http://juliaastro.github.io/FITSIO.jl/latest/index.html) or [FITS](https://github.com/JuliaAstro/FITSIO.jl) file or name of the FITS file. A keyword argument `hdu_out` can be given while using FITS or FITS file name to specify specific HDU in FITS file.
+WCS information is extracted from header when ImageHDU or FITS file is given as `output_projection`.
+
+Order of Interpolation can be specified by keyword `order` (i.e 0, 1(default), 2). 
+The dimensions of output Image can be given by keyword `shape_out`. This can be used to change resolution.
+
+
+Example
+-------
+```
+julia> using Reproject, FITSIO
+
+julia> input_data = FITS("gc_msx_e.fits)
+
+julia> output_projection = FITS("gc_2mass_k.fits")
+
+julia> result = reproject(input_data, output_projection, shape_out = (1000,1000), order = 2, hdu_in = 1, hdu_out = 1)
+```
+**Input Image:**
+<img name="community" src="Images/input.png"/>
+
+**Output:**
+<img name="community" src="Images/output.png"/>
+
+Test files can be obtained from [here](https://astropy.stsci.edu/data/).
+
+Related Packages
+-------
+Check out [AstroImages.jl](https://github.com/JuliaAstro/AstroImages.jl), which use this package to form coloured RGB image from 2D CCD Astromonical Images.
+
 License
 -------
 
 The `reproject` package is released under the terms of the BSD 3-Clause "New" or
 "Revised" License.  The `Reproject.jl` package received written permission to be
 released under the MIT "Expat" License.
+
+The authors of this package are [aquatiko](https://github.com/aquatiko) and [giordano](https://github.com/giordano).