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scaling PNGs with transparancy channel
#1

[eluser]stoefln[/eluser]
scaling regular images works great, but if i try to resize PNGs with transparency channel the channel is rendered black. why?

$config = array();
$config['image_library'] = 'gd2';
$config['source_image'] = $newPath.$newfilename;
$config['create_thumb'] = FALSE;
$config['maintain_ratio'] = TRUE;
$config['width'] = 100;
$config['height'] = 50;
$config['new_image'] = $thumbPath.$newfilename;
$this->load->library('image_lib', $config);
$this->image_lib->resize();
#2

[eluser]Josep Ma. Serra[/eluser]
did you finally solve that?

i was searching around and the GD library version that solves that bug its still a RC
#3

[eluser]stoefln[/eluser]
i used this function, it works great!

Code:
function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = 'file', $delete_original = true, $use_linux_commands = false )
    {
        if ( $height <= 0 && $width <= 0 ) {
            return false;
        }
        $info = getimagesize($file);
        $image = '';

        $final_width = 0;
        $final_height = 0;
        list($width_old, $height_old) = $info;

        if ($proportional) {
            if ($width == 0) $factor = $height/$height_old;
            elseif ($height == 0) $factor = $width/$width_old;
            else $factor = min ( $width / $width_old, $height / $height_old);  
            $final_width = round ($width_old * $factor);
            $final_height = round ($height_old * $factor);

        }
        else {      
            $final_width = ( $width <= 0 ) ? $width_old : $width;
            $final_height = ( $height <= 0 ) ? $height_old : $height;
        }

        switch ($info[2] ) {
            case IMAGETYPE_GIF:
                $image = imagecreatefromgif($file);
            break;
            case IMAGETYPE_JPEG:
                $image = imagecreatefromjpeg($file);
            break;
            case IMAGETYPE_PNG:
                $image = imagecreatefrompng($file);
            break;
            default:
                return false;
        }
      
        $image_resized = imagecreatetruecolor( $final_width, $final_height );
              
        if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
            $trnprt_indx = imagecolortransparent($image);
            // If we have a specific transparent color
            if ($trnprt_indx >= 0) {
                // Get the original image's transparent color's RGB values
                $trnprt_color    = imagecolorsforindex($image, $trnprt_indx);
                // Allocate the same color in the new image resource
                $trnprt_indx    = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $trnprt_indx);
                // Set the background color for new image to transparent
                imagecolortransparent($image_resized, $trnprt_indx);
            }
            // Always make a transparent background color for PNGs that don't have one allocated already
            elseif ($info[2] == IMAGETYPE_PNG) {
                // Turn off transparency blending (temporarily)
                imagealphablending($image_resized, false);
                // Create a new transparent color for image
                $color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
  
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $color);
  
                // Restore transparency blending
                imagesavealpha($image_resized, true);
            }
        }

        imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
  
        if ( $delete_original ) {
            if ( $use_linux_commands )
                exec('rm '.$file);
            else
                @unlink($file);
        }
      
        switch ( strtolower($output) ) {
            case 'browser':
                $mime = image_type_to_mime_type($info[2]);
                header("Content-type: $mime");
                $output = NULL;
            break;
            case 'file':
                $output = $file;
            break;
            case 'return':
                return $image_resized;
            break;
            default:
            break;
        }

        switch ($info[2] ) {
            case IMAGETYPE_GIF:
                imagegif($image_resized, $output);
            break;
            case IMAGETYPE_JPEG:
                imagejpeg($image_resized, $output);
            break;
            case IMAGETYPE_PNG:
                imagepng($image_resized, $output);
            break;
            default:
                return false;
        }

        return true;
    }
#4

[eluser]Josep Ma. Serra[/eluser]
Simply great, it works perfect!!!

Many thanks for that!

CI guys, could you integrate that functionality on the next release?
#5

[eluser]Nanto Mago[/eluser]
[quote author="stoefln" date="1228994600"]i used this function, it works great!

Code:
function smart_resize_image( $file, $width = 0, $height = 0, $proportional = false, $output = 'file', $delete_original = true, $use_linux_commands = false )
    {
        if ( $height <= 0 && $width <= 0 ) {
            return false;
        }
        $info = getimagesize($file);
        $image = '';

        $final_width = 0;
        $final_height = 0;
        list($width_old, $height_old) = $info;

        if ($proportional) {
            if ($width == 0) $factor = $height/$height_old;
            elseif ($height == 0) $factor = $width/$width_old;
            else $factor = min ( $width / $width_old, $height / $height_old);  
            $final_width = round ($width_old * $factor);
            $final_height = round ($height_old * $factor);

        }
        else {      
            $final_width = ( $width <= 0 ) ? $width_old : $width;
            $final_height = ( $height <= 0 ) ? $height_old : $height;
        }

        switch ($info[2] ) {
            case IMAGETYPE_GIF:
                $image = imagecreatefromgif($file);
            break;
            case IMAGETYPE_JPEG:
                $image = imagecreatefromjpeg($file);
            break;
            case IMAGETYPE_PNG:
                $image = imagecreatefrompng($file);
            break;
            default:
                return false;
        }
      
        $image_resized = imagecreatetruecolor( $final_width, $final_height );
              
        if ( ($info[2] == IMAGETYPE_GIF) || ($info[2] == IMAGETYPE_PNG) ) {
            $trnprt_indx = imagecolortransparent($image);
            // If we have a specific transparent color
            if ($trnprt_indx >= 0) {
                // Get the original image's transparent color's RGB values
                $trnprt_color    = imagecolorsforindex($image, $trnprt_indx);
                // Allocate the same color in the new image resource
                $trnprt_indx    = imagecolorallocate($image_resized, $trnprt_color['red'], $trnprt_color['green'], $trnprt_color['blue']);
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $trnprt_indx);
                // Set the background color for new image to transparent
                imagecolortransparent($image_resized, $trnprt_indx);
            }
            // Always make a transparent background color for PNGs that don't have one allocated already
            elseif ($info[2] == IMAGETYPE_PNG) {
                // Turn off transparency blending (temporarily)
                imagealphablending($image_resized, false);
                // Create a new transparent color for image
                $color = imagecolorallocatealpha($image_resized, 0, 0, 0, 127);
  
                // Completely fill the background of the new image with allocated color.
                imagefill($image_resized, 0, 0, $color);
  
                // Restore transparency blending
                imagesavealpha($image_resized, true);
            }
        }

        imagecopyresampled($image_resized, $image, 0, 0, 0, 0, $final_width, $final_height, $width_old, $height_old);
  
        if ( $delete_original ) {
            if ( $use_linux_commands )
                exec('rm '.$file);
            else
                @unlink($file);
        }
      
        switch ( strtolower($output) ) {
            case 'browser':
                $mime = image_type_to_mime_type($info[2]);
                header("Content-type: $mime");
                $output = NULL;
            break;
            case 'file':
                $output = $file;
            break;
            case 'return':
                return $image_resized;
            break;
            default:
            break;
        }

        switch ($info[2] ) {
            case IMAGETYPE_GIF:
                imagegif($image_resized, $output);
            break;
            case IMAGETYPE_JPEG:
                imagejpeg($image_resized, $output);
            break;
            case IMAGETYPE_PNG:
                imagepng($image_resized, $output);
            break;
            default:
                return false;
        }

        return true;
    }
[/quote]

How to define the output,

Code:
$this->smartresizeimage->smart_resize_image($path_image.$data['image'],
                              $width              = 450,
                              $height             = 0,
                              $proportional       = true,
                              $output = base_url()."public/image/",
                              $delete_original    = false,
                              $use_linux_commands = false );

but I got error message

Message: imagepng() [function.imagepng]: Unable to open 'http://localhost/project/public/image' for writing: No such file or directory

Filename: libraries/Smartresizeimage.php

Line Number: 90

#6

[eluser]CroNiX[/eluser]
did you create the public/image directory and give it write permissions?
#7

[eluser]Nanto Mago[/eluser]
[quote author="CroNiX" date="1348599794"]did you create the public/image directory and give it write permissions?[/quote]

yes of course. but any folder I try, I got same error.
#8

[eluser]CroNiX[/eluser]
Your path needs to be a filesystem path, NOT a url...
#9

[eluser]Nanto Mago[/eluser]
[quote author="CroNiX" date="1348600316"]Your path needs to be a filesystem path, NOT a url...[/quote]

can you give an example. How to define a fylesystem path on this output.
because I try like this

Code:
$output = base_url()."public/image/",

or

Code:
$output = "./public/image/",

I still got the same error
#10

[eluser]CroNiX[/eluser]
I usually use
FCPATH . 'public/image/'

assuming the "public" dir is at the same level as your index.php

It produces a full path and not a relative one.




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