base64 encoded identicon

    function identicon($stringToHash, $size = 32, $alt = '') {

        $hash = md5($stringToHash);

        $csh=hexdec(substr($hash,0,1)); // corner sprite shape
        $ssh=hexdec(substr($hash,1,1)); // side sprite shape
        $xsh=hexdec(substr($hash,2,1))&7; // center sprite shape

        $cro=hexdec(substr($hash,3,1))&3; // corner sprite rotation
        $sro=hexdec(substr($hash,4,1))&3; // side sprite rotation
        $xbg=hexdec(substr($hash,5,1))%2; // center sprite background

        /* corner sprite foreground color */
        $cfr=hexdec(substr($hash,6,2));
        $cfg=hexdec(substr($hash,8,2));
        $cfb=hexdec(substr($hash,10,2));

        /* side sprite foreground color */
        $sfr=hexdec(substr($hash,12,2));
        $sfg=hexdec(substr($hash,14,2));
        $sfb=hexdec(substr($hash,16,2));

        /* final angle of rotation */
        $angle=hexdec(substr($hash,18,2));

        /* size of each sprite */
        $spriteZ=128;

        /* start with blank 3x3 identicon */
        $identicon=imagecreatetruecolor($spriteZ*3,$spriteZ*3);
        imageantialias($identicon,TRUE);

        /* assign white as background */
        $bg=imagecolorallocate($identicon,255,255,255);
        imagefilledrectangle($identicon,0,0,$spriteZ,$spriteZ,$bg);

        /* generate corner sprites */
        $corner=getsprite($spriteZ,$csh,$cfr,$cfg,$cfb,$cro);
        imagecopy($identicon,$corner,0,0,0,0,$spriteZ,$spriteZ);
        $corner=imagerotate($corner,90,$bg);
        imagecopy($identicon,$corner,0,$spriteZ*2,0,0,$spriteZ,$spriteZ);
        $corner=imagerotate($corner,90,$bg);
        imagecopy($identicon,$corner,$spriteZ*2,$spriteZ*2,0,0,$spriteZ,$spriteZ);
        $corner=imagerotate($corner,90,$bg);
        imagecopy($identicon,$corner,$spriteZ*2,0,0,0,$spriteZ,$spriteZ);

        /* generate side sprites */
        $side=getsprite($spriteZ,$ssh,$sfr,$sfg,$sfb,$sro);
        imagecopy($identicon,$side,$spriteZ,0,0,0,$spriteZ,$spriteZ);
        $side=imagerotate($side,90,$bg);
        imagecopy($identicon,$side,0,$spriteZ,0,0,$spriteZ,$spriteZ);
        $side=imagerotate($side,90,$bg);
        imagecopy($identicon,$side,$spriteZ,$spriteZ*2,0,0,$spriteZ,$spriteZ);
        $side=imagerotate($side,90,$bg);
        imagecopy($identicon,$side,$spriteZ*2,$spriteZ,0,0,$spriteZ,$spriteZ);

        /* generate center sprite */
        $center=getcenter($spriteZ,$xsh,$cfr,$cfg,$cfb,$sfr,$sfg,$sfb,$xbg);
        imagecopy($identicon,$center,$spriteZ,$spriteZ,0,0,$spriteZ,$spriteZ);

        // $identicon=imagerotate($identicon,$angle,$bg);

        /* make white transparent */
        imagecolortransparent($identicon,$bg);

        /* create blank image according to specified dimensions */
        $resized=imagecreatetruecolor($size,$size);
        imageantialias($resized,TRUE);

        /* assign white as background */
        $bg=imagecolorallocate($resized,255,255,255);
        imagefilledrectangle($resized,0,0,$size,$size,$bg);

        /* resize identicon according to specification */
        imagecopyresampled($resized,$identicon,0,0,(imagesx($identicon)-$spriteZ*3)/2,(imagesx($identicon)-$spriteZ*3)/2,$size,$size,$spriteZ*3,$spriteZ*3);

        /* make white transparent */
        imagecolortransparent($resized,$bg);

        ob_start();
        imagepng($resized);
        $image = ob_get_clean();

        return '<img src="data:image/png;base64,' . base64_encode($image) .
            '" alt="' . $alt .
            '"' . (!empty($alt) ? ' title="' . $alt . '"' : '') .
            ' width="' . $size . '" height="' . $size . '" />';

        imagedestroy($resized);
    }

    function getsprite($spriteZ,$shape,$R,$G,$B,$rotation) {
        $sprite=imagecreatetruecolor($spriteZ,$spriteZ);
        imageantialias($sprite,TRUE);
        $fg=imagecolorallocate($sprite,$R,$G,$B);
        $bg=imagecolorallocate($sprite,255,255,255);
        imagefilledrectangle($sprite,0,0,$spriteZ,$spriteZ,$bg);
        switch($shape) {
            case 0: // triangle
                $shape=array(
                    0.5,1,
                    1,0,
                    1,1
                );
                break;
            case 1: // parallelogram
                $shape=array(
                    0.5,0,
                    1,0,
                    0.5,1,
                    0,1
                );
                break;
            case 2: // mouse ears
                $shape=array(
                    0.5,0,
                    1,0,
                    1,1,
                    0.5,1,
                    1,0.5
                );
                break;
            case 3: // ribbon
                $shape=array(
                    0,0.5,
                    0.5,0,
                    1,0.5,
                    0.5,1,
                    0.5,0.5
                );
                break;
            case 4: // sails
                $shape=array(
                    0,0.5,
                    1,0,
                    1,1,
                    0,1,
                    1,0.5
                );
                break;
            case 5: // fins
                $shape=array(
                    1,0,
                    1,1,
                    0.5,1,
                    1,0.5,
                    0.5,0.5
                );
                break;
            case 6: // beak
                $shape=array(
                    0,0,
                    1,0,
                    1,0.5,
                    0,0,
                    0.5,1,
                    0,1
                );
                break;
            case 7: // chevron
                $shape=array(
                    0,0,
                    0.5,0,
                    1,0.5,
                    0.5,1,
                    0,1,
                    0.5,0.5
                );
                break;
            case 8: // fish
                $shape=array(
                    0.5,0,
                    0.5,0.5,
                    1,0.5,
                    1,1,
                    0.5,1,
                    0.5,0.5,
                    0,0.5
                );
                break;
            case 9: // kite
                $shape=array(
                    0,0,
                    1,0,
                    0.5,0.5,
                    1,0.5,
                    0.5,1,
                    0.5,0.5,
                    0,1
                );
                break;
            case 10: // trough
                $shape=array(
                    0,0.5,
                    0.5,1,
                    1,0.5,
                    0.5,0,
                    1,0,
                    1,1,
                    0,1
                );
                break;
            case 11: // rays
                $shape=array(
                    0.5,0,
                    1,0,
                    1,1,
                    0.5,1,
                    1,0.75,
                    0.5,0.5,
                    1,0.25
                );
                break;
            case 12: // double rhombus
                $shape=array(
                    0,0.5,
                    0.5,0,
                    0.5,0.5,
                    1,0,
                    1,0.5,
                    0.5,1,
                    0.5,0.5,
                    0,1
                );
                break;
            case 13: // crown
                $shape=array(
                    0,0,
                    1,0,
                    1,1,
                    0,1,
                    1,0.5,
                    0.5,0.25,
                    0.5,0.75,
                    0,0.5,
                    0.5,0.25
                );
                break;
            case 14: // radioactive
                $shape=array(
                    0,0.5,
                    0.5,0.5,
                    0.5,0,
                    1,0,
                    0.5,0.5,
                    1,0.5,
                    0.5,1,
                    0.5,0.5,
                    0,1
                );
                break;
            default: // tiles
                $shape=array(
                    0,0,
                    1,0,
                    0.5,0.5,
                    0.5,0,
                    0,0.5,
                    1,0.5,
                    0.5,1,
                    0.5,0.5,
                    0,1
                );
                break;
        }
        /* apply ratios */
        for ($i=0;$i<count($shape);$i++)
            $shape[$i]=$shape[$i]*$spriteZ;
        imagefilledpolygon($sprite,$shape,count($shape)/2,$fg);
        /* rotate the sprite */
        for ($i=0;$i<$rotation;$i++)
            $sprite=imagerotate($sprite,90,$bg);
        return $sprite;
    }

    /* generate sprite for center block */
    function getcenter($spriteZ,$shape,$fR,$fG,$fB,$bR,$bG,$bB,$usebg) {
        $sprite=imagecreatetruecolor($spriteZ,$spriteZ);
        imageantialias($sprite,TRUE);
        $fg=imagecolorallocate($sprite,$fR,$fG,$fB);
        /* make sure there's enough contrast before we use background color of side sprite */
        if ($usebg>0 && (abs($fR-$bR)>127 || abs($fG-$bG)>127 || abs($fB-$bB)>127))
            $bg=imagecolorallocate($sprite,$bR,$bG,$bB);
        else
            $bg=imagecolorallocate($sprite,255,255,255);
        imagefilledrectangle($sprite,0,0,$spriteZ,$spriteZ,$bg);
        switch($shape) {
            case 0: // empty
                $shape=array();
                break;
            case 1: // fill
                $shape=array(
                    0,0,
                    1,0,
                    1,1,
                    0,1
                );
                break;
            case 2: // diamond
                $shape=array(
                    0.5,0,
                    1,0.5,
                    0.5,1,
                    0,0.5
                );
                break;
            case 3: // reverse diamond
                $shape=array(
                    0,0,
                    1,0,
                    1,1,
                    0,1,
                    0,0.5,
                    0.5,1,
                    1,0.5,
                    0.5,0,
                    0,0.5
                );
                break;
            case 4: // cross
                $shape=array(
                    0.25,0,
                    0.75,0,
                    0.5,0.5,
                    1,0.25,
                    1,0.75,
                    0.5,0.5,
                    0.75,1,
                    0.25,1,
                    0.5,0.5,
                    0,0.75,
                    0,0.25,
                    0.5,0.5
                );
                break;
            case 5: // morning star
                $shape=array(
                    0,0,
                    0.5,0.25,
                    1,0,
                    0.75,0.5,
                    1,1,
                    0.5,0.75,
                    0,1,
                    0.25,0.5
                );
                break;
            case 6: // small square
                $shape=array(
                    0.33,0.33,
                    0.67,0.33,
                    0.67,0.67,
                    0.33,0.67
                );
                break;
            case 7: // checkerboard
                $shape=array(
                    0,0,
                    0.33,0,
                    0.33,0.33,
                    0.66,0.33,
                    0.67,0,
                    1,0,
                    1,0.33,
                    0.67,0.33,
                    0.67,0.67,
                    1,0.67,
                    1,1,
                    0.67,1,
                    0.67,0.67,
                    0.33,0.67,
                    0.33,1,
                    0,1,
                    0,0.67,
                    0.33,0.67,
                    0.33,0.33,
                    0,0.33
                );
                break;
        }
        /* apply ratios */
        for ($i=0;$i<count($shape);$i++)
            $shape[$i]=$shape[$i]*$spriteZ;
        if (count($shape)>0)
            imagefilledpolygon($sprite,$shape,count($shape)/2,$fg);
        return $sprite;
    }