Average Image Color in php for png/jpeg

Question

I want to calculate the average color of an image (png or jpg) in php.

I want a little script that will go fast to calculate the average color.

I tried by resizing an image to 1px by 1px but I didn't have success. I always have an error like this : imagesx() expects parameter 1 to be resource, string given in

Here is my php:

$post_thumb   = wp_get_attachment_url( get_post_thumbnail_id() );   
$img = $post_thumb;
$x = imagesx($img);
$y = imagesy($img);
$tmp_img = ImageCreateTrueColor(1,1);
ImageCopyResampled($tmp_img,$img,0,0,0,0,1,1,$x,$y);
$rgb = ImageColorAt($tmp_img,0,0);

I know it comes from my image var but I don't know how to resolve it...

Answer 1

Lolo, this is the function I use to have the average color of a picture

function average($img) 
{
    $w = imagesx($img);
    $h = imagesy($img);
    $r = $g = $b = 0;
    for($y = 0; $y < $h; $y += 2) {
        for($x = 0; $x < $w; $x++) {
            $rgb = imagecolorat($img, $x, $y);
            $r += $rgb >> 16;
            $g += $rgb >> 8 & 255;
            $b += $rgb & 255;
        }
    }
    $pxls = $w * $h;
    $r = dechex(round($r / $pxls));
    $g = dechex(round($g / $pxls));
    $b = dechex(round($b / $pxls));
    if(strlen($r) < 2) {
        $r = 0 . $r;
    }
    if(strlen($g) < 2) {
        $g = 0 . $g;
    }
    if(strlen($b) < 2) {
        $b = 0 . $b;
    }
    return "#" . $r . $g . $b;
}

Answer 2

I'v got it, it was a problem from my var object:

$img = @imagecreatefromstring(file_get_contents($post_thumb));
$x = imagesx($img);
$y = imagesy($img);
$tmp_img = ImageCreateTrueColor(1,1);
ImageCopyResampled($tmp_img,$img,0,0,0,0,1,1,$x,$y);
$rgb = ImageColorAt($tmp_img,0,0);
$r   = ($rgb >> 16) & 0xFF;
$g = ($rgb >> 8) & 0xFF;
$b  =  $rgb & 0xFF;