Some more README nonsense

README.md

@@ -3,6 +3,12 @@
 FitsPHP (or `fits-php`) is a dumb and crappy "library" to somehow interact with the FITS image format used in astronomy.  
 The library tries to implement a reasonable subset of the [FITS standard](https://fits.gsfc.nasa.gov/fits_standard.html). Of course, it all depends on the definition of 'reasonable'...
 
+It should allow for the image to be displayed in a browser or even a terminal (yeah, right...).
+
+## Why
+
+Why not? But seriously, this doesn't make any sense, you should never use it in any circumstance whatsoever! The idea for this terrible endeavour came from [a video by Dylan O'Donnell](https://youtube.com).
+
 ## Usage
 
 Add the package with Composer:
@@ -11,11 +17,12 @@ Add the package with Composer:
 composer require dumbastro/fits-php
 ```
 
-then use classes from the `Dumbastro\FitsPhp` namespace.
+then use classes from the `Dumbastro\FitsPhp` namespace. More info in the documentation.
 
 ### Examples
 
-Retrieve the image blob for a given FITS file then do something with the bytes:
+Retrieve the image blob for a given FITS file then do something with the bytes.  
+The method `ImageBlob::dataBytes` returns a `Generator`.
 
 ```php
 <?php
@@ -33,6 +40,39 @@ foreach ($blob->dataBytes() as $byte) {
 }
 ```
 
-The method `ImageBlob::dataBytes` returns a `Generator`.
+Read a specific keyword value from the FITS header. In this example, `BITPIX` is read which represents the bit depth (bits per pixel) of the image. The bitpix is also a property of the image blob, represented by a PHP `Enum`. Calling the `type()` method on the property returns a string with the following possible values (assuming the bitpix is valid in the first place):
 
+|Bitpix value|Type string|Interpretation|
+-------------|-----------|--------------|
+|    8      | `int8`  |Character or unsigned binary integer|
+|   16      | `int16` |16 bit two's complement binary integer|
+|   32      | `int32` |32 bit two's complement binary integer|
+|   64      | `int64` |64 bit two's complement binary integer|
+|   -32     |`float32`|IEEE single-precision floating point|
+|   -64     |`float64`|IEEE double-precision floating point|
 
+```php
+<?php
+
+declare(strict_types=1);
+
+use Dumbastro\FitsPhp\Fits;
+use Dumbastro\FitsPhp\FitsHeader;
+
+$fits = new Fits('bubble_nebula.fit'); // Bit-depth is 32-bit unsigned (for example)
+$fitsHeader = new FitsHeader($fits->headerBlock);
+$bitpix = (int) $fitsHeader->keyword('BITPIX')->value;
+
+// Or, with the image blob
+$blob = new ImageBlob($header, $fits->imageBlob);
+echo $blob->bitpix->type(); //int32
+
+```
+
+## TODO
+
+- [x] Read keywords from the FITS header
+- [x] Separate the main data table (actual image data) from the header (partly done? Who knows...)
+- []  Actually display the image in the standard output
+- []  Save the image to PNG and JPG
+- []  Manipulate the bits using basic processing algorithms??