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Change image color to transparent using GD library

Change image color to transparent using GD library. The base color and the offset are the incoming parameters.


						

function color2transparent($filepath, $colorToConvert=255, $offset=20, $overwrite=0){

    

    if(!is_file($_SERVER["DOCUMENT_ROOT"] . $filepath)){

        return("File not found, please check filepath!!");

    }

    $fileInfo = pathinfo($filepath);

    $oldfile = $_SERVER["DOCUMENT_ROOT"] . $filepath;

    $newfile = $_SERVER["DOCUMENT_ROOT"] . $fileInfo[dirname] . "/transp_.png";



    if(!is_file($newfile) || $overwrite){

        $im = imagecreatefromjpeg($oldfile);

        imagetruecolortopalette($im, true, 256);

        

        $total = imagecolorstotal( $im );

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

            $index = imagecolorsforindex( $im, $i );

            $red    = ($index["red"]  >= ($colorToConvert-$offset) || $index["red"]   >= ($colorToConvert+$offset))?$colorToConvert:$index["red"];

            $green  = ($index["green"]>= ($colorToConvert-$offset) || $index["green"] >= ($colorToConvert+$offset))?$colorToConvert:$index["green"];

            $blue   = ($index["blue"] >= ($colorToConvert-$offset) || $index["blue"]  >= ($colorToConvert+$offset))?$colorToConvert:$index["blue"];

            imagecolorset( $im, $i, $red, $green, $blue );

        }

        

        $size = getimagesize($oldfile);

        $img = imagecreatetruecolor($size[0],$size[1]);

        $trans = imagecolorallocate($img, 255, 255, 255);

        imagecolortransparent($img,$trans);

        imagecopy($img,$im,0,0,0,0,$size[0],$size[1]);

        imagetruecolortopalette($img, true, 256);

        imageinterlace($img);

        imagepng($img,$newfile);

        imagedestroy($img);

    }

    

    return($fileInfo[dirname] . "/" . basename($newfile));

    

} 
						
					

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