forked from kennethrapp/phasher
/
dct.php
133 lines (106 loc) · 3.1 KB
/
dct.php
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<?php
function grayscale($img){
if(function_exists('imagefilter')){
imagefilter($img, IMG_FILTER_GRAYSCALE);
return $img;
}
else{
$imgw = imagesx($img);
$imgh = imagesy($img);
for ($i=0; $i<$imgw; $i++){
for ($j=0; $j<$imgh; $j++){
$rgb = imagecolorat($img, $i, $j);
$rr = ($rgb >> 16) & 0xFF;
$gg = ($rgb >> 8) & 0xFF;
$bb = $rgb & 0xFF;
$g = round(($rr + $gg + $bb) / 3);
$val = imagecolorallocate($img, $g, $g, $g);
imagesetpixel ($img, $i, $j, $val);
}
}
return $img;
}
}
function resizetosquare($img_original, $size){
$img = imagecreatetruecolor($size, $size);
imagecopyresized($img, $img_original, 0, 0, 0, 0, $size, $size, imagesx($img_original), imagesy($img_original));
return $img;
}
// discrete cosine transform by jey http://stackoverflow.com/users/1976843/jey
// http://stackoverflow.com/questions/14106984/how-to-calculate-discrete-cosine-transform-dct-in-php
function dct1D($in){
$results = array();
$N = count($in);
for($k = 0; $k < $N; $k++){
$sum = 0;
for($n = 0; $n < $N; $n++){
$sum += $in[$k] * cos($k * pi() * (2 * $n + 1) / $N);
}
$sum *= sqrt(2 / $N);
if($k == 0){
$sum *= 1 / sqrt(2);
}
$results[$k] = $sum;
}
return $results;
}
function optimizedImgDTC($img){
$results = array();
$N1 = imagesx($img);
$N2 = imagesy($img);
$rows = array();
$row = array();
for($j = 0; $j < $N2; $j++){
for($i = 0; $i < $N1; $i++)
$row[$i] = imagecolorat($img, $i, $j);
$rows[$j] = dct1D($row);
}
for($i = 0; $i < $N1; $i++){
for($j = 0; $j < $N2; $j++)
$col[$j] = $rows[$j][$i];
$results[$i] = dct1D($col);
}
return $results;
}
function array_average($arr){
return array_sum($arr)/count($arr);
}
function pHashWithDCT($file){
$hash=array();
$image = imagecreatefromstring(file_get_contents($file));
$image = resizetosquare($image, 8);
$image = grayscale($image);
$dct = optimizedImgDTC($image);
foreach($dct as $key=>$val){
$avg = array_average($val);
foreach($dct[$key] as $bit=>$bit_val){
if($bit_val < $avg){
array_push($hash, 0);
}
else{
array_push($hash, 1);
}
}
}
return $hash;
}
function hashAsImage($phash, $w=64, $h=64, $cell=8, $rgb_on = array(0,255,0), $rgb_off=array(0,0,0), $type='image/png'){
$image = imagecreatetruecolor($w, $h);
$white = imagecolorallocate($image, $rgb_on[0], $rgb_on[1], $rgb_on[2]);
$black = imagecolorallocate($image, $rgb_off[0], $rgb_off[1], $rgb_off[2]);
imagefill($image, 0, 0, $black);
for($x = 0; $x < $w; $x+=$cell){
for($y=0; $y < $h; $y+=$cell){
$bit = array_shift($phash);
if($bit === 1){
imagefilledrectangle($image, $x, $y, $x+$cell, $y+$cell, $white);
}
}
}
return $image;
}
$image = "demo/monalisa.jpg";
$hash = pHashWithDCT($image);
$name = md5_file($image).'.jpg';
imagejpeg(hashAsImage($hash, 64, 64, 8), $name);
echo '<img src="'.$image.'"> <img src="'.$name.'">';