Imagick::getImageScene
The getImageSignature function returns the SHA-256 hash value, which is 256 bits (or 32 bytes) in length. SHA-256 is part of the SHA-2 set of cryptographic hash functions designed by the NSA, which also includes SHA-224, SHA-384, and SHA-512. According to Wikipedia, there are some security flaws in it similar to the set of SHA-1 hash functions, which should be fixed with SHA-3, eventually. Unlike MD5 or the SHA-1 set of cryptographic functions, SHA-2 has had no collisions discovered yet (a collision is an incident where two different pieces of data result in the same hash value from the hashing function). For the time being, it seems to be the most efficient method for creating a small (32-byte), uniquely-identifiable, generally-secure value for either a file or a piece of data.
Some sample code :
<?php
// Author: holdoffhunger@gmail.com
// Imagick Type
// ---------------------------------------------
$imagick_type = new Imagick();
// Open File
// ---------------------------------------------
$file_to_grab = "image_workshop_directory/test.bmp";
$file_handle_for_viewing_image_file = fopen($file_to_grab, 'a+');
// Grab File
// ---------------------------------------------
$imagick_type->readImageFile($file_handle_for_viewing_image_file);
// Get Image SHA-256 Signature / Hash Value
// ---------------------------------------------
$imagick_type_signature = $imagick_type->getImageSignature();
// Print Image Signature / Hash Value
// ---------------------------------------------
print($imagick_type_signature);
?>
Results of this done on a standard BMP image :
cb2f387a7b23d11340ad1f5ba9c765125ea6b2d50a0d25412abe1ce568adac68
Imagick::getImageSignature
(PECL imagick 2.0.0)
Imagick::getImageSignature — Generates an SHA-256 message digest
Description
string Imagick::getImageSignature
( void
)
Generates an SHA-256 message digest for the image pixel stream.
Return Values
Returns a string containing the SHA-256 hash of the file.
Errors/Exceptions
Throws ImagickException on error.
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User Contributed Notes
Imagick::getImageSignature
holdoffhunger at gmail dot com
20-May-2012 04:30