84 lines
2.8 KiB
Markdown
84 lines
2.8 KiB
Markdown
# FitsPHP - A dumb FITS image library for PHP
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FitsPHP (or `fits-php`) is a dumb and crappy "library" to somehow interact with the FITS image format used in astronomy.
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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'...
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It should allow for the image to be displayed in a browser or even a terminal (yeah, right...).
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## Why
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Why not? But seriously, this doesn't make any sense, you should never use it in any circumstance whatsoever!
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## Usage
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**NOTE: Not added to Packagist yet...**
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Add the package with Composer:
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```
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composer require dumbastro/fits-php
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```
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then use classes from the `Dumbastro\FitsPhp` namespace.
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### Examples
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Retrieve the image blob for a given FITS file then do something with the bytes.
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The method `ImageBlob::dataBytes` returns a `Generator`.
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```php
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<?php
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declare(strict_types=1);
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use Dumbastro\FitsPhp\Fits;
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use Dumbastro\FitsPhp\ImageBlob;
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$fits = new Fits('bubble_nebula.fit');
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$blob = new ImageBlob($fits->header(), $fits->imageBlob);
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foreach ($blob->dataBytes() as $byte) {
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// Do something useful...
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}
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```
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Read a specific keyword value from the FITS header. In this example, `BITPIX` is read which represents the bit depth (bits per pixel) of the image. The bitpix is also a property of the image blob, represented by a PHP `Enum`. Calling the `type()` method on the property returns a string with the following possible values (assuming the bitpix is valid in the first place):
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|Bitpix value|Type string|Interpretation|
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-------------|-----------|--------------|
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| 8 | `int8` |Character or unsigned binary integer|
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| 16 | `int16` |16 bit two's complement binary integer|
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| 32 | `int32` |32 bit two's complement binary integer|
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| 64 | `int64` |64 bit two's complement binary integer|
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| -32 |`float32`|IEEE single-precision floating point|
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| -64 |`float64`|IEEE double-precision floating point|
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```php
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<?php
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declare(strict_types=1);
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use Dumbastro\FitsPhp\Fits;
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use Dumbastro\FitsPhp\FitsHeader;
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use Dumbastro\FitsPhp\ImageBlob;
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$fits = new Fits('bubble_nebula.fit'); // Bit-depth is 32-bit unsigned (for example)
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$fitsHeader = new FitsHeader($fits->headerBlock);
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$bitpix = (int) $fitsHeader->keyword('BITPIX')->value;
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// Or, with the image blob
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$blob = new ImageBlob($header, $fits->imageBlob);
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echo $blob->bitpix->type(); //int32
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```
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## TODO
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- [x] Separate the main data table (actual image data) from the header (partly done? Who knows...)
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- [x] Read keywords from the FITS header (COMMENT keywords could be buggy)
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- [ ] History keywords?
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- [ ] FITS extensions?
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- [ ] Actually display the image in the standard output
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- [ ] Save the image to PNG and/or JPG
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- [ ] Manipulate the bits using basic processing algorithms??
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