hash()
hash(\Grafika\Gd\Image $image, \Grafika\Gd\Editor $editor) : string
Generate and get the average hash of the image.
Parameters
| \Grafika\Gd\Image | $image | |
| \Grafika\Gd\Editor | $editor |
AverageHash
Algorithm: Reduce size. Remove high frequencies and detail by shrinking to 8x8 so that there are 64 total pixels. Reduce color. The tiny 8x8 picture is converted to a grayscale. Average the colors. Compute the mean value of the 64 colors. Compute the bits. Each bit is simply set based on whether the color value is above or below the mean. Construct the hash. Set the 64 bits into a 64-bit integer. The order does not matter, just as long as you are consistent.
http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html
hash(\Grafika\Gd\Image $image, \Grafika\Gd\Editor $editor) : string
Generate and get the average hash of the image.
| \Grafika\Gd\Image | $image | |
| \Grafika\Gd\Editor | $editor |
<?php
namespace Grafika\Gd\ImageHash;
use Grafika\Gd\Editor;
use Grafika\Gd\Image;
/**
* AverageHash
*
* Algorithm:
* Reduce size. Remove high frequencies and detail by shrinking to 8x8 so that there are 64 total pixels.
* Reduce color. The tiny 8x8 picture is converted to a grayscale.
* Average the colors. Compute the mean value of the 64 colors.
* Compute the bits. Each bit is simply set based on whether the color value is above or below the mean.
* Construct the hash. Set the 64 bits into a 64-bit integer. The order does not matter, just as long as you are consistent.
*
* http://www.hackerfactor.com/blog/index.php?/archives/432-Looks-Like-It.html
*
* @package Grafika\Gd\ImageHash
*/
class AverageHash
{
/**
* Generate and get the average hash of the image.
*
* @param Image $image
*
* @param Editor $editor
*
* @return string
*/
public function hash($image, $editor)
{
// Resize the image.
$width = 8;
$height = 8;
$image = clone $image; // Make sure we are working on the clone if Image is passed
$editor->resizeExact($image, $width, $height); // Resize to exactly 8x8
$gd = $image->getCore();
// Create an array of greyscale pixel values.
$pixels = array();
for ($y = 0; $y < $height; $y++) {
for ($x = 0; $x < $width; $x++) {
$rgba = imagecolorat($gd, $x, $y);
$r = ($rgba >> 16) & 0xFF;
$g = ($rgba >> 8) & 0xFF;
$b = $rgba & 0xFF;
$pixels[] = floor(($r + $g + $b) / 3); // Gray
}
}
// Get the average pixel value.
$average = floor(array_sum($pixels) / count($pixels));
// Each hash bit is set based on whether the current pixels value is above or below the average.
$hash = '';
foreach ($pixels as $pixel) {
if ($pixel > $average) {
$hash .= '1';
} else {
$hash .= '0';
}
}
return $hash;
}
}