imageconvolution

Last updated: Fri, 22 Aug 2008

imagecolortransparent

(PHP 4, PHP 5)

imagecolortransparent — Define uma cor como tansparente

Descrição

int imagecolortransparent ( resource $image [, int $color ] )

Define a cor transparente na dada image .

Parâmetros

image: An image resource, returned by one of the image creation functions, such as imagecreatetruecolor().
color: Um identificador de cor criado com imagecolorallocate()

Valor Retornado

O identificador da nova (ou atual, se nenhuma for especificada) cor transparente é retornado.

Notas

Nota: A transparência é copiada apenas com imagecopymerged() e imagens true color, não com imagecopy() ou imagens de paleta.

Nota: A cor transparente é uma propriedade da imagem, a transparencia não é uma propriedade da cor. Uma vez que você definiu uma cor para ser a cor de transparência, todas as regiões da imagem que eram desenhadas com esta cor anteriormente serão transparentes.

imageconvolution

imagecolorstotal

Last updated: Fri, 22 Aug 2008

add a note User Contributed Notes
imagecolortransparent

cca220v
11-Sep-2008 11:47


I found out the hard way that for two png's with alpha transparency to correctly stack you need to explicitly re-enable alpha blending.



$img=imagecreatetruecolor($dx,$dy);

$img1=imagecreatefrompng($png1); //first layer

$img2=imagecreatefrompng($png2); //second layer (smaller image)



imagealphablending($img, false);

$transparent = imagecolorallocatealpha($img, 0, 0, 0, 127);

imagefill($img, 0, 0, $transparent);

imagesavealpha($img,true);

imagealphablending($img, true); //removing this causes the second layer's transparency to go trough the 1st layer erasing it (the image >is< transparent there ... as is the 2nd layer ... but not the 1st so it should not be transparent)



imagecopyresampled($img,$img1,

imagecopyresampled($img,$img2,

yousuf at philipz dot com
01-Apr-2008 09:45


Well 8-bit gif and png files can have multiple transparent colors, so detecting the transparent color by manually looking into the file or using imagecolortransparent and using the detected rgb color as the background color when imagecopy'ing (or other image copying functions) on a true color image will not work. The only means of getting the transparent pixels to appear is to copy the pixel colors one by one to a new true color image. Here's some code i wrote to do this.



$original_image = @imagecreatefromgif( $original_image_file );



$original_image_width = imagesx( $original_image );

$original_image_height = imagesy( $original_image );



if ( !imageistruecolor($original_image) ) {

   # detects if its non-true color image

   if ( imagecolortransparent($original_image) >= 0 ) {

      # detects if any of the color palette has been set to transparent

      $truecolor = imagecreatetruecolor( $original_image_width, $original_image_height );

      for ($x = 0; $x < $original_image_width; $x++) {

         for ($y = 0; $y < $original_image_height; $y++) {

            $color_index = ImageColorAt($original_image, $x, $y);

            if ( !$color_palette[$color_index] ) {

               $rgb = imagecolorsforindex($original_image, $color_index);

               $color_to_set = imagecolorallocate($truecolor, $rgb['red'], $rgb['green'], $rgb['blue']);

               $color_palette[$color_index] = $color_to_set;

            } else {

               $color_to_set = $color_palette[$color_index];

            }

            imagesetpixel($truecolor, $x, $y, $color_to_set);

         }

      }

      imagedestroy($original_image);

      $original_image = $truecolor;

   }

}

kroccamen, gmail
27-Mar-2008 02:56


Sorry, below should be:



<?php

$is_alpha = ord (file_get_contents ($file_path, false, null, 25, 1)) & 4;

?>



much better :)

Both types 4 (greyscale transparent png), and 6 (colour transparent png) have bit 4 set, so there's no need to bitwise twice and there's no need for == as the return value will be 4 or 0, which is easily interpreted as true or false elsewhere in your code.



note: file_get_contents isn't reading the whole file in this instance, just 1 byte on its own and that's it, so you can be assured this is fast and safe.

kroccamen, gmail
25-Mar-2008 01:44


@wesley gunn:

Thank you very, very much for the code to determine if a PNG is 24 or 32-bit :)

Here's an improved version in one line without using a file-handle



<?php

$is_alpha = ((ord (

    file_get_contents ($filename, false, null, 25, 1)

) & 6) & 4) == 4;

?>



Gives true for a PNG with alpha, false otherwise.

This cannot detect 8-bit PNGs with transparency, but you could do that by searching the file contents for the presence of "PLTE" *AND* "tRNS".

tomas at cimax dot com
10-Mar-2008 09:19


On some versions you must set the index number of that color in color pallete rather than the color! So if you allocate color with imagecolorallocate, that this color gets 0 index on color pallete so than you must call: imagecolortransparent ( resource $image , 0 ) to make the image transparent!

Anonymous
28-Feb-2008 11:52


I came across some images that have transparent color allocated even if they don't have any transparent pixels (transparent color is unused).

fmkaiba at optonline dot net
07-Feb-2008 05:05


This is my 'perfect' (i use that word lightly) thumbnail generation script, switch '$transparency' to true to have it do its best to handle transparency in gifs and pngs. this code is built off of comments and advice of everyone else here, and i do not deserve full credit. So far this handles every error i can throw at it.

<?php

function createthumb($name, $newname, $new_w, $new_h, $border=false, $transparency=true, $base64=false) {

    if(file_exists($newname))

        @unlink($newname);

    if(!file_exists($name))

        return false;

    $arr = split("\.",$name);

    $ext = $arr[count($arr)-1];



    if($ext=="jpeg" || $ext=="jpg"){

        $img = @imagecreatefromjpeg($name);

    } elseif($ext=="png"){

        $img = @imagecreatefrompng($name);

    } elseif($ext=="gif") {

        $img = @imagecreatefromgif($name);

    }

    if(!$img)

        return false;

    $old_x = imageSX($img);

    $old_y = imageSY($img);

    if($old_x < $new_w && $old_y < $new_h) {

        $thumb_w = $old_x;

        $thumb_h = $old_y;

    } elseif ($old_x > $old_y) {

        $thumb_w = $new_w;

        $thumb_h = floor(($old_y*($new_h/$old_x)));

    } elseif ($old_x < $old_y) {

        $thumb_w = floor($old_x*($new_w/$old_y));

        $thumb_h = $new_h;

    } elseif ($old_x == $old_y) {

        $thumb_w = $new_w;

        $thumb_h = $new_h;

    }

    $thumb_w = ($thumb_w<1) ? 1 : $thumb_w;

    $thumb_h = ($thumb_h<1) ? 1 : $thumb_h;

    $new_img = ImageCreateTrueColor($thumb_w, $thumb_h);

    

    if($transparency) {

        if($ext=="png") {

            imagealphablending($new_img, false);

            $colorTransparent = imagecolorallocatealpha($new_img, 0, 0, 0, 127);

            imagefill($new_img, 0, 0, $colorTransparent);

            imagesavealpha($new_img, true);

        } elseif($ext=="gif") {

            $trnprt_indx = imagecolortransparent($img);

            if ($trnprt_indx >= 0) {

                //its transparent

                $trnprt_color = imagecolorsforindex($img, $trnprt_indx);

                $trnprt_indx = imagecolorallocate($new_img, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);

                imagefill($new_img, 0, 0, $trnprt_indx);

                imagecolortransparent($new_img, $trnprt_indx);

            }

        }

    } else {

        Imagefill($new_img, 0, 0, imagecolorallocate($new_img, 255, 255, 255));

    }

    

    imagecopyresampled($new_img, $img, 0,0,0,0, $thumb_w, $thumb_h, $old_x, $old_y); 

    if($border) {

        $black = imagecolorallocate($new_img, 0, 0, 0);

        imagerectangle($new_img,0,0, $thumb_w, $thumb_h, $black);

    }

    if($base64) {

        ob_start();

        imagepng($new_img);

        $img = ob_get_contents();

        ob_end_clean();

        $return = base64_encode($img);

    } else {

        if($ext=="jpeg" || $ext=="jpg"){

            imagejpeg($new_img, $newname);

            $return = true;

        } elseif($ext=="png"){

            imagepng($new_img, $newname);

            $return = true;

        } elseif($ext=="gif") {

            imagegif($new_img, $newname);

            $return = true;

        }

    }

    imagedestroy($new_img); 

    imagedestroy($img); 

    return $return;

}

//example useage

createthumb("img.gif", "tn_img.gif", 64,64,true, true, false);

?>

wesley dot gunn at email dot it
13-Nov-2007 06:27


a simple way to check png with alpha channel reading IHDR PNG HEADER



$readPng =    fopen    ($argSourceImagePath, "rb");

$readAlp =    fread    ($readPng, 52);

            fclose    ($readPng);



if(substr(bin2hex($readAlp),50,2) == "04" || substr(bin2hex($readAlp),50,2) == "06")

echo("Png has alpha");

Rob
09-Oct-2007 04:55


This block of code should preserve transparency when resizing an image using the GD library.



<?php

/**

 * Try to preserve transparency info

 * $orig_type - Original Image Type

 * $orig_img  - GD Image Resource for original image

 * $new_img   - GD Image Resource for resized image

 */



// Transparency only available for GIFs & PNGs

if ( ($orig_type == IMAGETYPE_GIF) || ($orig_type == IMAGETYPE_PNG) ) {

    $trnprt_indx = imagecolortransparent($orig_img);



    // If we have a specific transparent color

    if ($trnprt_indx >= 0) {



        // Get the original image's transparent color's RGB values

        $trnprt_color    = imagecolorsforindex($orig_img, $trnprt_indx);



        // Allocate the same color in the new image resource

        $trnprt_indx    = imagecolorallocate($new_img, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);



        // Completely fill the background of the new image with allocated color.

        imagefill($new_img, 0, 0, $trnprt_indx);



        // Set the background color for new image to transparent

        imagecolortransparent($new_img, $trnprt_indx);



    // Always make a transparent background color for PNGs that don't have one allocated already

    } elseif ($orig_type == IMAGETYPE_PNG) {



        // Turn off transparency blending (temporarily)

        imagealphablending($new_img, false);



        // Create a new transparent color for image

        $color = imagecolorallocatealpha($new_img, 0, 0, 0, 127);



        // Completely fill the background of the new image with allocated color.

        imagefill($this->new_img, 0, 0, $color);



        // Restore transparency blending

        imagesavealpha($this->new_img, true);

    }

}

?>

kevinoe at gmail
11-Sep-2007 10:39


To resize a transparent image into a thumbnail while keeping its transparency. The quality of the thumbnail is pretty bad though.. but it is transparent.



$image = ImageCreateFromGIF('transparentimage.gif');

$img_width = ImagesX($image);

$img_height = ImagesY($image);



$new_width = '100';

$new_height = ($new_width * $img_height) / $img_width;



$resized = imagecreatetruecolor($new_width, $new_height);



$colorTransparent = imagecolortransparent($image);

imagepalettecopy($image, $resized);

imagefill($resized, 0, 0, $colorTransparent);

imagecolortransparent($resized, $colorTransparent);



imagetruecolortopalette($resized, true, 256);



imagecopyresized($resized, $image, 0, 0, 0, 0, $new_width, $new_height, $img_width, $img_height);

Mikasto
15-Aug-2007 01:53


To resize transparent PNG (if image is transparent & ImageColorTransparent() returns -1):

1) create a new image with the new sizes

2) make the new image all transparent

3) turn off the alpha blending for the new image (to keep the alpha channel when copy data)

4) do copyresampled or copyresized into new image



PHP code:

// 1

$im2 = ImageCreateTrueColor($w, $h);

// 2

ImageColorTransparent($im2, ImageColorAllocate($im2, 0, 0, 0));

// 3

ImageAlphaBlending($im2, false);

// 4

ImageCopyResampled($im2, $im, 0, 0, 0, 0, $w, $h, ImageSX($im), ImageSY($im));

erik at vectorsector dot net
13-Jul-2007 06:20


This script creates transparency for a unspecific RBG color for an already created PNG image.  It also includes script of overlay text that does not get ruined in the process. 



<?php



header("Content-type: image/png");

$image = imagecreatetruecolor(250, 250);

$string = $_GET['text'];

$im     = imagecreatefrompng("dynIcon.png");

$img = imagecreatetruecolor(16,16);

$orange = imagecolorallocate($im, 220, 210, 60);

$bg_color = imagecolorat($im,1,1);

$px     = (imagesx($im) - 3 * strlen($string)) / 2;

imagecolortransparent($im, $bg_color);

imagestring($im, 3, $px, 5, $string, $orange);

imagepng($im);

imagedestroy($im);



?> 



Use $bg_color = imagecolorat($im,1,1); for instance, if you made the transparent color in photoshop by clearing out all the color leaving you with the checkered background showing you it's empty.

cinymini
14-Dec-2006 08:17


When you use palette images (created with imagecreate()), the first color allocated is the background color. This color cannot be used for transparency. So if you want to make the background transparent, first allocate a dummy background color, then allocate the real background color and declare this is as transparent.

glenn at bengeweb dot co dot nz
18-Nov-2006 05:03


in reference to webmaster at webnetwizard dotco dotuk who had a rather complicated method of determining if a GIF had any transparency set ...



imagecolortransparent will return -1 if no transparency is found.



eg:



$transColorIndexMain = imageColorTransparent($mainImgObj);

if ($transColorIndexMain >= 0 ) {

       # GIF has transparency ... ;

}



Current PHP Version: 4.4.4

[GD Version] => bundled (2.0.28 compatible)

Blaine Ehrhart
07-Jul-2006 11:59


This script creates transparency for a specific RBG color for an already created GIF image. 

<?php

    $im = imagecreatefromgif('trans.gif');

    $img = imagecreatetruecolor(16,16);

    $trans = imagecolorallocate($img,255,99,140);

    imagecolortransparent($img,$trans);

    imagecopy($img,$im,0,0,0,0,16,16);

    imagetruecolortopalette($img, true, 256);

    imageinterlace($img);

    imagegif($img,'trans.gif');

    imagedestroy($img);

?>

Joachim Kruyswijk
20-Oct-2005 01:20


A negative color number will turn antialiasing off, but even a positive number chosen for transparency may affect antialiasing. If the text (created with imagettftext) in your image looks horrible, try using a higher color number.

contact at wdschools dot com
19-Oct-2005 06:02


Transparent GIF w/ text from TTF Font

------------------------------------- 

$image = imagecreatetruecolor(192, 36);

$trans_color = imagecolorallocate($image, 255, 0, 0);

$color = imagecolorallocate($image, 255, 255, 255);

imagecolortransparent($image, $trans_color);

imagettftext($image, 10, 0, 10, 23, $color, "impact.ttf", " MENU ITEM");

imagegif($image, "output.gif");

imagedestroy($image);

ingrid
09-Jun-2005 06:37


This script should take an animated GIF whit a white background transparancy, put some white=transparant text on it, and can be used in any page using the filename and the normal image tags.



Everything works well, exept the animation. The GIF animation stands still. Don't know how to keep the animation  animated. Is it possible in PHP?



<?php



$TextFile = "teller.txt";

$Count = trim(file_get_contents($TextFile));

$FP = fopen($TextFile, "r");

$Count=fgets($FP, 4096);

fclose ($FP);

settype($Count, "integer");

$Count++;

if ($FP = fopen ($TextFile, "w")){

fwrite ($FP, $Count);

fclose ($FP);

}



$image = "blad.gif";

$im    = imagecreatefromgif($image);

$white = imageColorAllocate ($im, 255, 255, 255);

$trans = imagecolortransparent($im,$white);

$hit = "$Count";

$ip = $_SERVER["REMOTE_ADDR"];



ImageString($im, 2, 30, 60,  " je bent bezoeker ", $white);

ImageString($im, 3, 20, 80, " $ip.$hit", $trans);



header("Content-Type: image/gif");

Imagegif($im,'',100);

ImageDestroy ($im);



?>

thomas at nindel dot net
20-Apr-2005 07:02


I wanted to have non-rectangular images being displayed on various website-backgrounds. piece of cake with png-24 and sane browsers, but not with IE. GIF-files are useless since they tend to have ugly edges.



So that's what i came up with, a script to merge a given PNG-24 against a background-image. The script only merges areas of partial transparency (think anti-aliased edges) of the PNG onto the background-image, leaving 100% transparent areas as they are. output is a 256-color gif with transparency.



<?PHP

  function alphaishMerge(&$img_unten, &$img_oben, &$transCol) {

    $sx = imagesx($img_unten);

    $sy = imagesy($img_oben);

    

    // just be sure

    imagealphablending($img_unten, TRUE);

    imagealphablending($img_oben, TRUE);

    

    // imagecopy respects alpha channels

    imagecopy($img_unten, $img_oben, 0, 0, 0, 0, $sx, $sy);

    

    for ($x = 0; $x < $sx; $x++) {

      for ($y = 0; $y < $sy; $y++) {

        

        // get RGBA of upper image

        $pxloben = imagecolorat($img_oben, $x, $y);

        $pxloben = imagecolorsforindex($img_oben, $pxloben);

        

        if ($pxloben['alpha'] == 127) {

          // if this pixel is fully transparent...

          // ...set it to the transparent color 

          imagesetpixel($img_unten,$x,$y,$transCol);

        }

      }

    }

  }

  

  // images have to be the same size

  $bg_file = "background.jpg";

  $png_file ="kauscha.png";



  // background-image (jpg)

  $img_bg = imagecreatefromjpeg($bg_file);

  

  // image which is supposed to be put on the background (PNG-24)

  $img_png = imagecreatefrompng($png_file);

  

  // This color is the one getting transparent in the gif-file

  $transCol = imagecolorallocate($img_bg, 0, 0, 0);



  // magic

  alphaishMerge($img_bg, $img_png, $transCol);

  

  // reduce color depth

  imagetruecolortopalette($img_bg, FALSE, 255);

  

  // make it transparent

  $transCol = imagecolortransparent($img_bg, $transCol);

  

  header("Content-type: image/gif");

  imagegif($img_bg);

?>



i hope thats useful for anyone.

partyheld at HATESPAMgmail dot com
31-Mar-2005 07:35


Fred wrote:

<?php

$file['signatur']=      substr($result,0,3);

             $file['version']=        substr($result,3,3);

             $file['width']=          ord(substr($result,6,1))+ord(substr($result,7,1))*256;

             $file['height']=        ord(substr($result,8,1))+ord(substr($rsult,9,1))*256;

             $file['flag']=          ord(substr($result,10,1))>>7;

             $file['trans_red']=      ord(substr($result,ord(substr($result,11))*3,1));

             $file['trans_green']=    ord(substr($result,ord(substr($result,11))*3+1,1));

             $file['trans_blue']=    ord(substr($result,ord(substr($result,11))*3+2,1)) ;

?>



You should write such code like this:



<?php

   $file = array(

      "signatur"           => substr ($result, 0, 3),

      "version"            => substr ($result, 3, 3),

      "width"              => ord (substr ($result, 6, 1)) + ord (substr ($result, 7, 1)) * 256,

      "height"             => ord (substr ($result, 8, 1)) + ord(substr ($result, 9, 1)) * 256,

      "flag"               => ord (substr ($result, 10, 1)) >> 7,

      "trans_red"          => ord (substr ($result, ord (substr ($result, 11)) * 3,1)),

      "trans_green"        => ord (substr ($result, ord (substr($result, 11)) * 3 + 1, 1)),

      "trans_blue"         => ord (substr ($result, ord (substr($result, 11)) * 3 + 2, 1))

      );

?>



And there's a typo in line 4, sayin "rsult" instead of "result". I've got no time for checking your code any further, sorry.

raiserle
28-Mar-2005 06:52


it goes also more simply

i rather work with arrays

<?php

if(!function_exists('gif_info'))

{

    function gif_info($filename)

    {

             $fp=                     fopen($filename,'rb');

             $result=                 fread($fp,13);

             $file['signatur']=       substr($result,0,3);

             $file['version']=        substr($result,3,3);

             $file['width']=          ord(substr($result,6,1))+ord(substr($result,7,1))*256;

             $file['height']=         ord(substr($result,8,1))+ord(substr($rsult,9,1))*256;

             $file['flag']=           ord(substr($result,10,1))>>7;

             $file['trans_red']=      ord(substr($result,ord(substr($result,11))*3,1));

             $file['trans_green']=    ord(substr($result,ord(substr($result,11))*3+1,1));

             $file['trans_blue']=     ord(substr($result,ord(substr($result,11))*3+2,1)) ;

             fclose($fp);

             return $file;

    }

}

print_r(gif_info($_FILES['files']['temp_name']));

?>

talkback at codesponge dot com
17-Mar-2005 12:41


Only one color may be transparent in one image.  The last call to imagecolortransparent will be the color that is set to transparent.



I am processing button images that have a slightly different fill color than the background color outside the border of the button. I was hoping that I could just make both of those colors transparent and solve the problem.



Hope this tidbit of info will save you some time.

fred at webblake dot net
14-Jan-2005 05:17


Wow! I am actually surprized there are no functions to retrieve transparency information from the image. I assume I'm not missing anything since there are all kinds of notes about how to get around this limitation. At any rate, here is some code to read the gif file and retrieve the missing information. The code will speak volumes.



<?php



    class GifInfo

    {

        var $m_transparentRed;

        var $m_transparentGreen;

        var $m_transparentBlue;

        var $m_signature;

        var $m_version;

        var $m_width;

        var $m_height;

        var $m_width;

        var $m_height;

        var $m_colorFlag;

        var $m_backgroundIndex;

        

        

        function GifInfo($filename)

        {



            $fp                         = fopen($filename,"rb");

            $result                     = fread($fp,13);

            $this->m_signature     = substr($result,0,3);

            $this->m_version         = substr($result,3,3);

            $this->m_width         = ord(substr($result,6,1)) + ord(substr($result,7,1)) * 256;

            $this->m_height         = ord(substr($result,8,1)) + ord(substr($result,9,1)) * 256;

            $this->m_colorFlag    = ord(substr($result,10,1)) >> 7;

            $this->m_background     = ord(substr($result,11));

    

            if($this->m_colorFlag)

            {

                $tableSizeNeeded = ($this->m_background + 1) * 3;

                $result = fread($fp,$tableSizeNeeded);

                $this->m_transparentRed     = ord(substr($result,$this->m_background * 3,1));

                $this->m_transparentGreen     = ord(substr($result,$this->m_background * 3 + 1,1));        

                $this->m_transparentBlue     = ord(substr($result,$this->m_background * 3 + 2,1));            

            }

            fclose($fp);

        }

    }

?>



And to use this class....



<?php

   $size = getimagesize($userfile);



   $img2 = ImageCreate($w,$h);            

   $gi = new GifInfo($userfile);



   if($gi->m_version == '89a' && $gi->m_colorFlag == 1)

   {

      $transparent = imagecolorallocate($img2, 

      $gi->m_transparentRed,

      $gi->m_transparentGreen,

      $gi->m_transparentBlue);            



      imagecolortransparent ($img2,$transparent);

   }

?>

webmaster at webnetwizard dotco dotuk
11-Jan-2005 10:24


I'm feeling particularly altruistic today, so here is the code to accompany the text I submitted about a script that 'intelligently' detects if an uploaded GIF has transparency or not, and creates a thumbnail accordingly:



    if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile))

    {

      $note = "Image was successfully uploaded.\n";

      // Now create thumbnail version of the uploaded image and save it to

      // folder "$fixPath/images/thumbs". First, we need to create a

      // resource "handle" for a copy of the uploaded image

      $img_error = false;

      list($width, $height, $type) = getimagesize($uploadfile);

      switch($type) // Allowed types: image/gif,image/jpeg,image/x-png

      {

        case 1: // GIF

          $src = @imagecreatefromgif($uploadfile);

          if (!$src)

            $img_error = true;

          break;

        case 2: // JPEG

         .

         .

         .

      case 3: // PNG

        .

        .

        . 

       default:

          $img_error = true;

      }

      // resource handle for source image now in $src

      // Now calculate scaling factor and put in $sf

      if(!$img_error)

      {

        if($width >= $height && $width > 100)

          $sf = $width / 100;

        elseif($height > 100)

          $sf = $height / 100;

        else

          $sf = 1;

        $newwidth = intval($width / $sf);

        $newheight = intval($height / $sf);

  

        switch($type) // Allowed types: image/gif,image/jpeg,image/x-png

        {

          case 1: // GIF

            $tpcolor = imagecolorat($src, 0, 0);

            // in the real world, you'd better test all four corners, not just one!

            $dest = imagecreate($newwidth, $newheight);

            // $dest automatically has a black fill...

            imagepalettecopy($dest, $src);

            imagecopyresized($dest, $src, 0, 0, 0, 0, $newwidth, $newheight,

              $width, $height);

            $pixel_over_black = imagecolorat($dest, 0, 0);

            // ...but now make the fill white...

            $bg = imagecolorallocate($dest, 255, 255, 255);

            imagefilledrectangle($dest, 0, 0, $newwidth, $newheight,

              $bg);

            imagecopyresized($dest, $src, 0, 0, 0, 0, $newwidth, $newheight,

              $width, $height);

            $pixel_over_white = imagecolorat($dest, 0, 0);

            // ...to test if transparency causes the fill color to show through:

            if($pixel_over_black != $pixel_over_white)

            {

              // Background IS transparent

              imagefilledrectangle($dest, 0, 0, $newwidth, $newheight,

                $tpcolor);

              imagecopyresized($dest, $src, 0, 0, 0, 0, $newwidth,

                $newheight, $width, $height);

              imagecolortransparent($dest, $tpcolor);

              imagegif($dest, "$fixPath/images/thumbs/$userfile");

            }

            else // Background (most probably) NOT transparent

              imagegif($dest, "$fixPath/images/thumbs/$userfile");

            break;

          case 2: // JPEG

          .

          .

          .

          case 3: // PNG

          .

          .

          .

            break;

        }

        imagedestroy($src);

        imagedestroy($dest);

      }

      else

        $note = "Error: Uploaded image but could not create thumbnail";

      header("location: $fixPath/index.php?next=$next&nb=$nb&userfile=$userfile");

    }

    else

      $note = "Could not find anything to upload\n";

webmaster at webnetwizard dotco dotuk
11-Jan-2005 03:09


After much devious mindbending, I have found a way to test any GIF for presence of background transparency. This ability is essential for my application which uploads any of GIF, JPEG or PNG and simultaneously creates a thumbnail of identical image type and identical filename (full size and thumbnail versions being stored in different folders).

After uploading and moving the image in the usual way, a switch($image_type) statement ensures that the optimum code is used to generate the thumbnail; regardless of image type.

The problem with the GIF type is that those with transparent backgrounds need to be treated differently to those without. When I don't detect GIF transparency, I either end up with all transparent GIF's having black backgrounds, or all GIF's get converted to transparent background - even if they weren't transparent in the original.

But how to detect transparency in the original? It finally occurred to me that I could test for transparency programmatically by overlaying a copy of the original image over an all-black image, record the color value at particular pixel locations and then repeat the process by overlaying a copy of the original image over an all-white image, recording the color values at identical pixel locations and comparing these with the first set of values.

If the two sets of values correlate exactly, and if sensible sampling points are used, the image can be treated as non-transparent. If the two sets of values show differences, the image should be treated as having a transparent background.

emilus at galeria-m dot art dot pl
30-Sep-2004 11:02


To resize or copy image (gif [with gd>=2.0.28] or png) with transparency.

-Take current transparency color

-create a new image with palette like old one and fill new image with transparent color

-set transparent color

-copy resized image



$colorTransparent = imagecolortransparent($im);

$im2 = imagecreate($new_w,$new_h);

imagepalettecopy($im2,$im);

imagefill($im2,0,0,$colorTransparent);

imagecolortransparent($im2, $colorTransparent);

imagecopyresized($im2,$im,0,0,0,0,$new_w,$new_h,$imsx,$imsy);

php_comment et 5mm de
27-Sep-2004 07:02


In fact this function can be used for two purposes:



A.) to work with transparency while dealing with images in php (see watermark example)



B.) to create a partially transparent picture



For A.) one can work with truecolor images with some regulations, but B.) can only be used with palette-based images (= indexed = created with imagecreate not imagecreatetruecolor) and formats that support transparency (png, gif).



For instance if you want to cut out a color out of a give picture that is in truecolor, use the following method to first convert it to palette-based image, assign the transparency and give it to the browser as png:



<?

$img = imagecreatefromjpeg('test.jpg');

imagetruecolortopalette($img, false, 256); // convert



$white = imagecolorresolve($img, 255, 255, 255); // resolve given palette entry

imagecolortransparent($img, $white);



header("Content-type: image/png");

imagepng($img);

?>

shelley_hina at yahoo dot com
04-Mar-2004 08:35


It took me a while to figure this out. I added visual web thumbnail preview graphic from http://www.thumbshots.org and http://www.thumbshots.com to my customer sites to visualize web pages. Then I needed to create a small blank transparent PNG image if the thumbshot is not available. You can do this easily using imagecolortransparent function. It came out really nice and fast. It's very cool stuff and highly recommended library for all your web site needs!



// Use GD library to create transparent color PNG image of the pixel size

$ImgGD = imagecreate(120, 90);

$ImgWhite = imagecolorallocate($ImgGD, 255, 255, 255);

imagefill($ImgGD, 0, 0, $ImgWhite);

imagecolortransparent($ImgGD, $ImgWhite);



// Capture STDOUT to buffer

ob_start();

imagepng($ImgGD);

$Image = ob_get_contents();

ob_end_clean();



// Remember to free your memory

imagedestroy($ImgGD);



// Print image to web browser.

print $Image

php at kybert dot com
14-Nov-2003 02:30


i had problems with the example by sandhawk at spies dot com because my png overlay, and the jpeg canvas were using different color depths, so, this function corrects this:



[code]

function WatermarkImage($CanvasImage, $WatermarkImage /* MUST BE PHG */, $Opacity=10, $Quality=75)

{

    // create true color canvas image:

    $canvas_src = imagecreatefromjpeg($CanvasImage);

    $canvas_w = ImageSX($canvas_src);

    $canvas_h = ImageSY($canvas_src);

    $canvas_img = imagecreatetruecolor($canvas_w, $canvas_h);

    imagecopy($canvas_img, $canvas_src, 0,0,0,0, $canvas_w, $canvas_h);

    imagedestroy($canvas_src);    // no longer needed



    // create true color overlay image:

    $overlay_src = imagecreatefrompng($WatermarkImage);

    $overlay_w = ImageSX($overlay_src);

    $overlay_h = ImageSY($overlay_src);

    $overlay_img = imagecreatetruecolor($overlay_w, $overlay_h);

    imagecopy($overlay_img, $overlay_src, 0,0,0,0, $overlay_w, $overlay_h);

    imagedestroy($overlay_src);    // no longer needed



    // setup transparent color (pick one):

    $black   = imagecolorallocate($overlay_img, 0x00, 0x00, 0x00);

    $white   = imagecolorallocate($overlay_img, 0xFF, 0xFF, 0xFF);

    $magenta = imagecolorallocate($overlay_img, 0xFF, 0x00, 0xFF);    

    // and use it here:

    imagecolortransparent($overlay_img, $white);



    // copy and merge the overlay image and the canvas image:

    imagecopymerge($canvas_img, $overlay_img, 0,0,0,0, $overlay_w, $overlay_h, $Opacity);



    // output:

    header("Content-type: image/jpeg");

    imagejpeg($canvas_img, '', $Quality);



    imagedestroy($overlay_img);

    imagedestroy($canvas_img);

}



// call function with opcity set to 50% and 95% quality

WatermarkImage("canvas.jpg", "overlay.png", 50, 95);



[/code]

creator79>>web>>de
09-Oct-2003 03:44


Hi!

I'm using GDLib 1.6.3 so far I know.

You can have transparency on any defined color on any image type when using the imagecolorclosest($im, $R, $G, $B) function instead of imagecolorallocate() or imagecolorexact().

calar at gamigo dot de
02-Aug-2003 03:53


ok some works...



i had a test-sytem with GDLib, phpinfo shows me this version:

"GD Version  2.0 or higher" so far no porblems with: imageColorTransparent



Then we had to copy ouer codes to another sever on this server phpinfo shots me version:

"GD Version  bundled (2.0.12 compatible)"



The jpg was wrong and nothing was transparent.

The point is, you have to use: imagecopymerge



Don't if its true on any system just work on 

SUSE 8.2

PHP 4.3.2

cladiniz at zipmail dot com dot br
18-Mar-2003 03:19


If you have a transparent PNG , in PHP 4.3.1 , GD 2.0 , you don't need to set the transparency anymore , it's automatic ...

sandhawk at spies dot com
06-Mar-2003 08:04


here's a little snippet of code that i got for getting images to overlay with transparency(based off text overlay above).



$olay_img = imagecreatefromPNG("overlay.png); //NOTE I recomment you use png for this, artifacts from jpeg images can look bad when you overlay them

$src_img = ImageCreateFromJPEG("image.jpg");

$src_w = ImageSX($src_img);

$src_h = ImageSY($src_img);



$can_img = imagecreatetruecolor($src_w, $src_h);



$black = ImageColorAllocate ($olay_img, 0, 0, 0);



ImageColorTransparent($olay_img, $black);



imagecopy($can_img, $src_img, 0,0,0,0, $src_w, $src_h);

imagecopymerge($can_img, $olay_img, 0,0,0,0, ImageSX($olay_img), ImageSY($olay_img),100); //Imagecopy won't work, you must used imagecopymerge



ImageJPEG($can_img,'',100);



imagedestroy($src_img);

imagedestroy($olay_img);

imagedestroy($can_img);

Jonatan
30-Dec-2002 07:35


I have found that ImageColorTransparent() works on true color images if and only if the transparent color is black.

(PHP 4.2.3/GD 2.0)

marshall.AT.byterage.net
05-May-2002 04:50


In response to the note above...



ImageColorTransparent() does work on TrueColor images.  I have it working myself but I do remember having to add an extra step somewhere.  Anyways, here is how I overlay text on a jpeg.  Don't forget, you need GD 2.x for true color to work.  This example requires TTF support also.



//

// get src image and dimensions

$src_img = ImageCreateFromJPEG("foo.jpg");

$src_w = ImageSX($src_img);

$src_h = ImageSY($src_img);

//

// create empty true color canvas, def bg is black

$txt_img = ImageCreateTrueColor($src_w,$src_h);

//

// define colors

$white = ImageColorAllocate ($txt_img, 255, 255, 255);

$black = ImageColorAllocate ($txt_img, 0, 0, 0);

//

// add your white text

ImageTTFText ($txt_img, 80, 25, 65, 350, $white, "impact.ttf", "Kung Fu");

//

// make black bg transparent

ImageColorTransparent($txt_img, $black);

//

// merge text image onto src image

ImageCopyMerge($src_img,$txt_img,0,0,0,0,$src_w,$src_h,30); // 30% opacity



'Now' you can do resizing or whatever and output it.  You need to create yet another blank image to resample.  (Actually you can resize the image before the text overlay step with some small mods, but its REALLY messy if you want the output size to be dynamic)



//

// create empty true color canvas for resizing.

$dst_img = ImageCreateTrueColor(100,100);

//

// resize

ImageCopyResampled($dst_img,$src_img,0,0,0,0,100,100,$src_w,$src_h); 

//

// output to browser.

ImageJPEG($dst_img,'',70);   // quality 70



If someone could tell me a shorter way to do this, that would be sweet.  The way it is now, it just feels like there is one too many steps to get this done.  But I am glad it works at all!

07-Dec-2001 04:18


when a color is defined as transparent, anytime that color is used in another function (before or after transparency definition) will be transparent





ex:


$red = ImageColorAllocate ($im, 233, 14, 91);


$blue = ImageColorAlloca