<?php
require('fpdf.php');

class PDF_ImageAlpha extends FPDF
{
//Private properties
var $tmpFiles = array(); 

/*******************************************************************************
*                                                                              *
*                               Public methods                                 *
*                                                                              *
*******************************************************************************/
function Image($file, $x=null, $y=null, $w=0, $h=0, $type='', $link='', $isMask=false, $maskImg=0)
{
    //Put an image on the page
    if(!isset($this->images[$file]))
    {
        //First use of this image, get info
        if($type=='')
        {
            $pos=strrpos($file,'.');
            if(!$pos)
                $this->Error('Image file has no extension and no type was specified: '.$file);
            $type=substr($file,$pos+1);
        }
        $type=strtolower($type);
        if($type=='png'){
            $info=$this->_parsepng($file);
            if($info=='alpha')
                return $this->ImagePngWithAlpha($file,$x,$y,$w,$h,$link);
        }
        else
        {
            if($type=='jpeg')
                $type='jpg';
            $mtd='_parse'.$type;
            if(!method_exists($this,$mtd))
                $this->Error('Unsupported image type: '.$type);
            $info=$this->$mtd($file);
        }
        if($isMask){
            if(in_array($file,$this->tmpFiles))
                $info['cs']='DeviceGray'; //hack necessary as GD can't produce gray scale images
            if($info['cs']!='DeviceGray')
                $this->Error('Mask must be a gray scale image');
            if($this->PDFVersion<'1.4')
                $this->PDFVersion='1.4';
        }
        $info['i']=count($this->images)+1;
        if($maskImg>0)
            $info['masked'] = $maskImg;
        $this->images[$file]=$info;
    }
    else
        $info=$this->images[$file];
    //Automatic width and height calculation if needed
    if($w==0 && $h==0)
    {
        //Put image at 72 dpi
        $w=$info['w']/$this->k;
        $h=$info['h']/$this->k;
    }
    elseif($w==0)
        $w=$h*$info['w']/$info['h'];
    elseif($h==0)
        $h=$w*$info['h']/$info['w'];
    //Flowing mode
    if($y===null)
    {
        if($this->y+$h>$this->PageBreakTrigger && !$this->InHeader && !$this->InFooter && $this->AcceptPageBreak())
        {
            //Automatic page break
            $x2=$this->x;
            $this->AddPage($this->CurOrientation,$this->CurPageFormat);
            $this->x=$x2;
        }
        $y=$this->y;
        $this->y+=$h;
    }
    if($x===null)
        $x=$this->x;
    if(!$isMask)
        $this->_out(sprintf('q %.2F 0 0 %.2F %.2F %.2F cm /I%d Do Q',$w*$this->k,$h*$this->k,$x*$this->k,($this->h-($y+$h))*$this->k,$info['i']));
    if($link)
        $this->Link($x,$y,$w,$h,$link);
    return $info['i'];
}

// needs GD 2.x extension
// pixel-wise operation, not very fast
function ImagePngWithAlpha($file,$x,$y,$w=0,$h=0,$link='')
{
    $tmp_alpha = tempnam('.', 'mska');
    $this->tmpFiles[] = $tmp_alpha;
    $tmp_plain = tempnam('.', 'mskp');
    $this->tmpFiles[] = $tmp_plain;

    list($wpx, $hpx) = getimagesize($file);
    $img = imagecreatefrompng($file);
    $alpha_img = imagecreate( $wpx, $hpx );

    // generate gray scale pallete
    for($c=0;$c<256;$c++)
        ImageColorAllocate($alpha_img, $c, $c, $c);

    // extract alpha channel
    $xpx=0;
    while ($xpx<$wpx){
        $ypx = 0;
        while ($ypx<$hpx){
            $color_index = imagecolorat($img, $xpx, $ypx);
            $col = imagecolorsforindex($img, $color_index);
            imagesetpixel($alpha_img, $xpx, $ypx, $this->_gamma( (127-$col['alpha'])*255/127) );
            ++$ypx;
        }
        ++$xpx;
    }

    imagepng($alpha_img, $tmp_alpha);
    imagedestroy($alpha_img);

    // extract image without alpha channel
    $plain_img = imagecreatetruecolor ( $wpx, $hpx );
    imagecopy($plain_img, $img, 0, 0, 0, 0, $wpx, $hpx );
    imagepng($plain_img, $tmp_plain);
    imagedestroy($plain_img);
    
    //first embed mask image (w, h, x, will be ignored)
    $maskImg = $this->Image($tmp_alpha, 0,0,0,0, 'PNG', '', true); 
    
    //embed image, masked with previously embedded mask
    $this->Image($tmp_plain,$x,$y,$w,$h,'PNG',$link, false, $maskImg);
}

function Close()
{
    parent::Close();
    // clean up tmp files
    foreach($this->tmpFiles as $tmp)
        @unlink($tmp);
}

/*******************************************************************************
*                                                                              *
*                               Private methods                                *
*                                                                              *
*******************************************************************************/
function _putimages()
{
    $filter=($this->compress) ? '/Filter /FlateDecode ' : '';
    reset($this->images);
    while(list($file,$info)=each($this->images))
    {
        $this->_newobj();
        $this->images[$file]['n']=$this->n;
        $this->_out('<</Type /XObject');
        $this->_out('/Subtype /Image');
        $this->_out('/Width '.$info['w']);
        $this->_out('/Height '.$info['h']);

        if(isset($info['masked']))
            $this->_out('/SMask '.($this->n-1).' 0 R');

        if($info['cs']=='Indexed')
            $this->_out('/ColorSpace [/Indexed /DeviceRGB '.(strlen($info['pal'])/3-1).' '.($this->n+1).' 0 R]');
        else
        {
            $this->_out('/ColorSpace /'.$info['cs']);
            if($info['cs']=='DeviceCMYK')
                $this->_out('/Decode [1 0 1 0 1 0 1 0]');
        }
        $this->_out('/BitsPerComponent '.$info['bpc']);
        if(isset($info['f']))
            $this->_out('/Filter /'.$info['f']);
        if(isset($info['parms']))
            $this->_out($info['parms']);
        if(isset($info['trns']) && is_array($info['trns']))
        {
            $trns='';
            for($i=0;$i<count($info['trns']);$i++)
                $trns.=$info['trns'][$i].' '.$info['trns'][$i].' ';
            $this->_out('/Mask ['.$trns.']');
        }
        $this->_out('/Length '.strlen($info['data']).'>>');
        $this->_putstream($info['data']);
        unset($this->images[$file]['data']);
        $this->_out('endobj');
        //Palette
        if($info['cs']=='Indexed')
        {
            $this->_newobj();
            $pal=($this->compress) ? gzcompress($info['pal']) : $info['pal'];
            $this->_out('<<'.$filter.'/Length '.strlen($pal).'>>');
            $this->_putstream($pal);
            $this->_out('endobj');
        }
    }
}

// GD seems to use a different gamma, this method is used to correct it again
function _gamma($v){
    return pow ($v/255, 2.2) * 255;
}

// this method overriding the original version is only needed to make the Image method support PNGs with alpha channels.
// if you only use the ImagePngWithAlpha method for such PNGs, you can remove it from this script.
function _parsepng($file)
{
    //Extract info from a PNG file
    $f=fopen($file,'rb');
    if(!$f)
        $this->Error('Can\'t open image file: '.$file);
    //Check signature
    if($this->_readstream($f,8)!=chr(137).'PNG'.chr(13).chr(10).chr(26).chr(10))
        $this->Error('Not a PNG file: '.$file);
    //Read header chunk
    $this->_readstream($f,4);
    if($this->_readstream($f,4)!='IHDR')
        $this->Error('Incorrect PNG file: '.$file);
    $w=$this->_readint($f);
    $h=$this->_readint($f);
    $bpc=ord($this->_readstream($f,1));
    if($bpc>8)
        $this->Error('16-bit depth not supported: '.$file);
    $ct=ord($this->_readstream($f,1));
    if($ct==0)
        $colspace='DeviceGray';
    elseif($ct==2)
        $colspace='DeviceRGB';
    elseif($ct==3)
        $colspace='Indexed';
    else {
        fclose($f);      // the only changes are 
        return 'alpha';  // made in those 2 lines
    }
    if(ord($this->_readstream($f,1))!=0)
        $this->Error('Unknown compression method: '.$file);
    if(ord($this->_readstream($f,1))!=0)
        $this->Error('Unknown filter method: '.$file);
    if(ord($this->_readstream($f,1))!=0)
        $this->Error('Interlacing not supported: '.$file);
    $this->_readstream($f,4);
    $parms='/DecodeParms <</Predictor 15 /Colors '.($ct==2 ? 3 : 1).' /BitsPerComponent '.$bpc.' /Columns '.$w.'>>';
    //Scan chunks looking for palette, transparency and image data
    $pal='';
    $trns='';
    $data='';
    do
    {
        $n=$this->_readint($f);
        $type=$this->_readstream($f,4);
        if($type=='PLTE')
        {
            //Read palette
            $pal=$this->_readstream($f,$n);
            $this->_readstream($f,4);
        }
        elseif($type=='tRNS')
        {
            //Read transparency info
            $t=$this->_readstream($f,$n);
            if($ct==0)
                $trns=array(ord(substr($t,1,1)));
            elseif($ct==2)
                $trns=array(ord(substr($t,1,1)), ord(substr($t,3,1)), ord(substr($t,5,1)));
            else
            {
                $pos=strpos($t,chr(0));
                if($pos!==false)
                    $trns=array($pos);
            }
            $this->_readstream($f,4);
        }
        elseif($type=='IDAT')
        {
            //Read image data block
            $data.=$this->_readstream($f,$n);
            $this->_readstream($f,4);
        }
        elseif($type=='IEND')
            break;
        else
            $this->_readstream($f,$n+4);
    }
    while($n);
    if($colspace=='Indexed' && empty($pal))
        $this->Error('Missing palette in '.$file);
    fclose($f);
    return array('w'=>$w, 'h'=>$h, 'cs'=>$colspace, 'bpc'=>$bpc, 'f'=>'FlateDecode', 'parms'=>$parms, 'pal'=>$pal, 'trns'=>$trns, 'data'=>$data);
}

}

?>