Using PHP to grab a simplified colour palette from an image? - php

Question

So far I have found examples on how to grab all the RGB values of each pixel in an image but I want something that will break down an image and give me a simplified color palette.
Is there a way to use imagetruecolortopalette to somehow spit out the reduced palette colours, or to break an image into 25 x 25 blocks and then grab the average value of that block?
Maybe there is an alternative I'm missing? I basically just want to be able to find the most common colors within an image.
Thanks in advance.

Answer 1

Hmm, well I have had created something like this for a client. The screenshot is below
The complete code is as follows
$microTime = microtime(true);
function textColor($R1, $G1, $B1) {
$a = (($R1 * 299) + ($G1 * 587 ) + ($B1 * 114 )) / 1000;
if ($a < 128)
return 'white';
else
return 'black';
}
function rgb2html($r, $g = -1, $b = -1) {
$hex = "#";
$hex.= str_pad(dechex($r), 2, "0", STR_PAD_LEFT);
$hex.= str_pad(dechex($g), 2, "0", STR_PAD_LEFT);
$hex.= str_pad(dechex($b), 2, "0", STR_PAD_LEFT);
return $hex;
if (is_array($r) && sizeof($r) == 3)
list($r, $g, $b) = $r;
$r = intval($r);
$g = intval($g);
$b = intval($b);
$r = dechex($r < 0 ? 0 : ($r > 255 ? 255 : $r));
$g = dechex($g < 0 ? 0 : ($g > 255 ? 255 : $g));
$b = dechex($b < 0 ? 0 : ($b > 255 ? 255 : $b));
$color = (strlen($r) < 2 ? '0' : '') . $r;
$color .= (strlen($g) < 2 ? '0' : '') . $g;
$color .= (strlen($b) < 2 ? '0' : '') . $b;
return '#' . $color;
}
function colorPalette($imageFile, $colorJump, $granularity = 5) {
$granularity = max(1, abs((int) $granularity));
$colors = array();
$ratio = array();
$wastageCount = array();
$occurrenceSCount = array();
$occurrenceMCount = array();
$size = #getimagesize($imageFile);
if ($size === false) {
return false;
}
$img = #imagecreatefromstring(file_get_contents($imageFile));
if (!$img) {
user_error("Unable to open image file");
return false;
}
for ($y = 0; $y < $size[1]; $y += $granularity) {
$lastColor = NULL;
$lastX = -1;
for ($x = 0; $x < $size[0]; $x += $granularity) {
$thisColor = imagecolorat($img, $x, $y);
$rgb = imagecolorsforindex($img, $thisColor);
$red = round(round(($rgb['red'] / $colorJump)) * $colorJump);
$green = round(round(($rgb['green'] / $colorJump)) * $colorJump);
$blue = round(round(($rgb['blue'] / $colorJump)) * $colorJump);
$thisRGB = $red . ',' . $green . ',' . $blue;
if ($lastColor != $thisRGB) {
if (array_key_exists($thisRGB, $wastageCount)) {
$wastageCount[$thisRGB]++;
} else {
$wastageCount[$thisRGB] = 1;
}
if ($lastX + 1 == $x) {
if (array_key_exists($lastColor, $occurrenceSCount)) {
$occurrenceSCount[$lastColor]++;
} else {
$occurrenceSCount[$lastColor] = 1;
}
}
if ($lastX + 1 != $x) {
if (array_key_exists($lastColor, $occurrenceMCount)) {
$occurrenceMCount[$lastColor]++;
} else {
$occurrenceMCount[$lastColor] = 1;
}
}
$lastColor = $thisRGB;
$lastX = $x;
}
if (array_key_exists($thisRGB, $colors)) {
$colors[$thisRGB]++;
} else {
$colors[$thisRGB] = 1;
}
}
}
$totalPixels = array_sum($colors);
foreach ($colors as $k => $v) {
$ratio[$k] = round(($v / $totalPixels ) * 100, 2);
}
return array($ratio, $wastageCount, $colors, $occurrenceSCount, $occurrenceMCount);
}
usage
$colorJump = 1;
$pixelJump = 1;
$paletteR = colorPalette($dbImgFile_dir, $colorJump, $pixelJump);
$palette = $paletteR[0];
$wastage = $paletteR[1];
$colorsFound = $paletteR[2];
$occSArray = $paletteR[3];
$occMArray = $paletteR[4];
$totalPixels = array_sum($colorsFound);
$totalTime = abs(microtime(true) - $microTime);
the looping around is more complex, as I have to get the pallet from the DB and to match the colors with them, and also the template parser is used which is full custom code, and will not help you.
Just ignore the Required Weight column from this, the single occurrences and multiple occurrences are calculated, if there is a single pixel, for example RED, RED, BLUE, RED, RED it will be 1 single occurrence and 2 multiple occurrence