I have a doubt in php.I wrote a php program to convert colour Images to
balck & white.It is working fine with JPEG files and PNG files.When it
comes to GIF files I am not getting the colour Image.I think I found
the reason of getting error.But I am not able to solve it
I am pasting the code which I wrote
The reason I think is when I am extracting the RGB value from the
image,R and G will be zero everytime.But I am getting the value of B.
As a Result I am getting a Black Box instead of Black and white Image
$file = 'logo2.gif';
header('Content-type: image/gif');
$imgtype = "gif";
list($width, $height) = getimagesize($f ile);
$source = imagecreatefrom gif($file);
$bwimage= imagecreate($wi dth, $height);
for ($c=0;$c<256;$c ++)
{
$palette[$c] = imagecoloralloc ate($bwimage,$c ,$c,$c);
}
function yiq($r,$g,$b)
{
return (($r*0.299)+($g *0.587)+($b*0.1 14));
}
for ($y=0;$y<$heigh t;$y++)
{
for ($x=0;$x<$width ;$x++)
{
$rgb = imagecolorat($s ource,$x,$y);
$r = ($rgb >16) & 0xFF;//error is here I am getting a value of zero
for $r and $g
$g = ($rgb >8) & 0xFF;//error getting the value zero everytime
$b = $rgb & 0xFF;//Here I am getting value
$gs = yiq($r,$g,$b);
imagesetpixel($ bwimage,$x,$y,$ palette[$gs]);
}
}
imagegif($bwima ge);
