PHP PNG image file parsing

Proud · 08-03-2004, 05:59 PM

Hi, I've just started messing with PHP and Apache, and knocked up the below quick script as a quirky idea. It's meant to read the hex colours of each pixel of a PNG file, and then print them as the colour for the background of a table division in a html page.

It does result in a grid of coloured cubes but my problem is the colour is wrong compared to the source image viewed enlarged in, say, the Gimp.

I suspect the problem lies in the int->hex code I copied from the PHP Manual, with the bitshifting and masking.

PHP Code:


			
<html>

<head>

<title>Pixel Picker</title>

</head>

<body>



<?php    

    $file = "/usr/share/icons/crystalsvg/32x32/apps/kmenu.png";

    $image = ImageCreateFromPng($file);

    $size = GetImageSize($file);

    $width = $size[0];

    $height = $size[1];

    

    echo "<table>";

    

    for ($i = 0; $i < $height; $i++) {

    

    echo "<tr>" ;

    

        for ($j = 0; $j < $width; $j++) {

        $rgb = ImageColorAt($image, $j, $i);

        $r = ($rgb >> 16) & 0xFF;

        $g = ($rgb >> 8) & 0xFF;

        $b = $rgb & 0xFF;



        echo "<td bgcolor=#";

        echo base_convert($r, 10, 16);

        echo base_convert($g, 10, 16);

        echo base_convert($b, 10, 16);

        echo "\">&nbsp&nbsp</td>";

        }

    

    echo "</tr>";

    }

    echo "</table>";

        ?>



</body>

</html>

Just wondering if anyone had a quick solution. Plus pointing out any bad coding habits would be appreciated.

hack124x768 · 08-03-2004, 06:10 PM

all i can think of would be that php may be set to only work with web standard colors, only 255. wheras your image may b in high, or true, colors, a lot more.

Proud · 08-04-2004, 12:20 PM

Well I improved the code and it works now well, except for not using the transparency values of the pixels.

PHP Code:


			
<html>

<head>

<title>Pixel Picker</title>

</head>

<body>



<?php    

    $file = "/usr/share/icons/crystalsvg/32x32/apps/kmenu.png";

    $image = ImageCreateFromPng($file);

    $size = GetImageSize($file);

    $width = $size[0];

    $height = $size[1];

    

    echo "<table>\n";

    

    for ($i = 0; $i < $height; $i++) {

    

    echo "<tr>\n" ;

    

        for ($j = 0; $j < $width; $j++) {

        $rgb = ImageColorAt($image, $j, $i);

        $r = ($rgb >> 16) & 0xFF;

        $g = ($rgb >> 8) & 0xFF;

        $b = $rgb & 0xFF;



        echo "<td bgcolor=\"#";

        $red = strtoupper(base_convert($r, 10, 16));

        $green = strtoupper(base_convert($g, 10, 16));

        $blue =  strtoupper(base_convert($b, 10, 16));

        

        if (strlen($red) == 1) {

        echo "0";

        echo $red;

        }

        else {

        echo $red;

        }

        if (strlen($green) == 1) {

        echo "0";

        echo $green;

        }

        else {

        echo $green;

        }

        if (strlen($blue) == 1) {

        echo "0";

        echo $blue;

        }

        else {

        echo $blue;

        }

        

        echo "\">&nbsp&nbsp</td>";

        }

    

    echo "\n</tr>\n";

    }

    echo "</table>\n";

        ?>



</body>

</html>

Cedrik · 08-04-2004, 12:34 PM

You can also short your code by replace your last if blocks by conditional statement like :

PHP Code:


			
//instead of:

if (strlen($red) == 1) {

        echo "0";

        echo $red;

} else {

        echo $red;

} 

// I would do:

echo (strlen($red) == 1) ? "0$red" : $red;

Proud · 08-04-2004, 12:55 PM

Nice! Thanks