a little something to replace in blackbart tip :
// start scanning (0=> black => empty)
$rleft = $w4 = $width<<2;
$rright = 0;
$rbottom = 0;
$rtop = $h4 = $height<<2;
for( $x = 0; $x < $w4; $x++ )
for( $y = 0; $y < $h4; $y++ )
if( imagecolorat( $img, $x, $y ) ){
$rleft = min( $rleft, $x );
$rright = max( $rright, $x );
$rtop = min( $rtop, $y );
$rbottom = max( $rbottom, $y );
}
with
// start scanning (0=> black => empty)
$break = false;
$rleft = $w4 = $width<<2;
$rright = 0;
$rbottom = 0;
$rtop = $h4 = $height<<2;
// scanning from left to right, breaking when a pixel is found, to scan from the other side : avoid scanning all pixels !
for($x=0; $x<$w4; $x++){
for($y=0; $y<$h4; $y++)
if(imagecolorat($img,$x,$y)){
$rtop = min($rtop, $y); $rleft = min($rleft, $x);
$break = true; break;
}
if($break) break;
}
// scanning from right to left, breaking when a pixel is found
for($x=($w4-1); $x>$rleft; $x--){
for($y=0; $y<$h4; $y++)
if(imagecolorat($img,$x,$y)){
$rright = max($rright, $x); $rbottom = max($rbottom, $y);
$break = true; break;
}
if($break) break;
}
//... //
it may be even better to check if the picture is portrait or landscape, to start the loops from left-right(landscape) or top-bottom (portrait)
