PHP: imagecreatefromjpeg

Description

resource imagecreatefromjpeg ( string filename )

imagecreatefromjpeg() returns an image identifier representing the image obtained from the given filename.

imagecreatefromjpeg() returns an empty string on failure. It also outputs an error message, which unfortunately displays as a broken link in a browser. To ease debugging the following example will produce an error JPEG:

Przykład 1. Example to handle an error during creation (courtesy vic at zymsys dot com )


<?php

function LoadJpeg($imgname) 

{

    $im = @imagecreatefromjpeg($imgname); /* Attempt to open */

    if (!$im) { /* See if it failed */

        $im  = imagecreate(150, 30); /* Create a blank image */

        $bgc = imagecolorallocate($im, 255, 255, 255);

        $tc  = imagecolorallocate($im, 0, 0, 0);

        imagefilledrectangle($im, 0, 0, 150, 30, $bgc);

        /* Output an errmsg */

        imagestring($im, 1, 5, 5, "Error loading $imgname", $tc);

    }

    return $im;

}

?>

Notatka: Obsługa JPEG jest dostępna tylko jeśli PHP zostało skompilowane z GD-1.8 lub nowszym.

Podpowiedź: Jeśli włączona jest dyrektywa konfiguracyjna fopen wrappers, możliwe jest podanie jako nazwy pliku adresu URL. Zobacz opis funkcji fopen() aby dowiedzieć się jak przekazać nazwę pliku, oraz fopen wrappers aby uzyskać listę obsługiwanych protokołów.

Ostrzeżenie

PHP w wersji starszej niż 4.3.0, pracujące pod kontrolą systemów Windows, nie obsługują dostępu do zdalnych plików w tej funkcji, nawet jeśli opcja allow_url_fopen jest włączona.

User Contributed Notes


In addition to yaroukh at gmail dot com comment.



It seems that even a small image can eat up your default memory limit real quick. Config value 'memory_limit' is marked PHP_INI_ALL, so you can change it dynamically using ini_set. Therefore, we can "allocate memory dynamically", to prevent those memory limit exceeded errors. 



<?php



$imageInfo = getimagesize('PATH/TO/YOUR/IMAGE');

$memoryNeeded = round(($imageInfo[0] * $imageInfo[1] * $imageInfo['bits'] * $imageInfo['channels'] / 8 + Pow(2, 16)) * 1.65);

                    

if (function_exists('memory_get_usage') && memory_get_usage() + $memoryNeeded > (integer) ini_get('memory_limit') * pow(1024, 2)) {

                        

    ini_set('memory_limit', (integer) ini_get('memory_limit') + ceil(((memory_get_usage() + $memoryNeeded) - (integer) ini_get('memory_limit') * pow(1024, 2)) / pow(1024, 2)) . 'M');

                        

}



?>


In running 4.3. Found out that jpegs generated by Canon PowerShot S70's cause imagecreatefromjpeg() to crash PHP [page cannot be displayed]. Made this function to check for it:

<?php

function check_s70($filename) {

        $thereturn = false;

        $handle = fopen($filename, "r");

        $contents = fread($handle, 159);

        fclose($handle);

        if (substr($contents, 156, 3) == "S70") {

            $thereturn = true;

        }

        return $thereturn;

    }

?>


Estimated memory needed for ImageCreateFromJPEG



First I supposed simple width*height*bpp will be enough, it isn't though; there is some pretty big overhead.



$imageInfo = GetImageSize($imageFilename);

$memoryNeeded = Round(($imageInfo[0] * $imageInfo[1] * $imageInfo['bits'] * $imageInfo['channels'] / 8 + Pow(2, 16)) * 1.65);



With memory_limit enabled running out of memory causes script to crash; above written will tel you how much memory you're gonna need for creating an image-resource out of image-file. So in conjunction with Memory_Get_Usage() and Get_CFG_Var('memory_limit') you can avoid the mentioned ending. (Yet there won't be too many images blocked from processing that would still fit in the memory, as the results of this are pretty accurate.)


here is a code, inspired by the button of

tl at comvironment dot com



but here, you can make as many buttons as you need by cutting the image in as many parts as defined in the table



<?php

class Button_Array{

    var $tab_button = array();// the text of each button you want to create

    var $im;//the image file

    

    function Button_Array($fileName, $tab_string){

        $this -> tab_button = $tab_string;

        $this -> im = $fileName;

        

        //parameters

        $font  = 10;



        //cut the full image in X parts

        //X = the number of buttons you want

         $imgFull=ImageCreateFromJPEG($this -> im);

         list($width, $heightFull, $type, $attr) = getimagesize($this -> im);

         

         $height = round($heightFull/sizeof($this->tab_button),0);



        

        for ($i=0;$i<sizeof($this->tab_button);$i++ ) {



            $pos=$i*$height;

            

            $imgParts[$i]=ImageCreateTrueColor($width,$height);

            if(imagecopy($imgParts[$i],$imgFull,0,0,0,$pos,$width,$height)){

            

                //manips

                $textColor = imagecolorallocate ($imgParts[$i],0,20,90);    

                ImageString ($imgParts[$i],$font,200,10,$this->tab_button[$i],$textColor);

                

                //cr