Proyectos de Subversion Moodle

<?php

// This file is part of Moodle - http://moodle.org/

//

// Moodle is free software: you can redistribute it and/or modify

// it under the terms of the GNU General Public License as published by

// the Free Software Foundation, either version 3 of the License, or

// (at your option) any later version.

//

// Moodle is distributed in the hope that it will be useful,

// but WITHOUT ANY WARRANTY; without even the implied warranty of

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

// GNU General Public License for more details.

//

// You should have received a copy of the GNU General Public License

// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**

 * Library code for manipulating PDFs

 *

 * @package assignfeedback_editpdf

 * @copyright 2012 Davo Smith

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

namespace assignfeedback_editpdf;

use setasign\Fpdi\TcpdfFpdi;

defined('MOODLE_INTERNAL') || die();

global $CFG;

require_once($CFG->libdir.'/pdflib.php');

require_once($CFG->dirroot.'/mod/assign/feedback/editpdf/fpdi/autoload.php');

/**

 * Library code for manipulating PDFs

 *

 * @package assignfeedback_editpdf

 * @copyright 2012 Davo Smith

 * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later

 */

class pdf extends TcpdfFpdi {

    /** @var int the number of the current page in the PDF being processed */

    protected $currentpage = 0;

    /** @var int the total number of pages in the PDF being processed */

    protected $pagecount = 0;

    /** @var float used to scale the pixel position of annotations (in the database) to the position in the final PDF */

    protected $scale = 0.0;

    /** @var string the path in which to store generated page images */

    protected $imagefolder = null;

    /** @var string the path to the PDF currently being processed */

    protected $filename = null;

    /** @var string the fontname used when the PDF being processed */

    protected $fontname = null;

    /** No errors */

    const GSPATH_OK = 'ok';

    /** Not set */

    const GSPATH_EMPTY = 'empty';

    /** Does not exist */

    const GSPATH_DOESNOTEXIST = 'doesnotexist';

    /** Is a dir */

    const GSPATH_ISDIR = 'isdir';

    /** Not executable */

    const GSPATH_NOTEXECUTABLE = 'notexecutable';

    /** Test file missing */

    const GSPATH_NOTESTFILE = 'notestfile';

    /** Any other error */

    const GSPATH_ERROR = 'error';

    /** Min. width an annotation should have */

    const MIN_ANNOTATION_WIDTH = 5;

    /** Min. height an annotation should have */

    const MIN_ANNOTATION_HEIGHT = 5;

    /** Blank PDF file used during error. */

    const BLANK_PDF = '/mod/assign/feedback/editpdf/fixtures/blank.pdf';

    /** Page image file name prefix*/

    const IMAGE_PAGE = 'image_page';

    /**

     * Get the name of the font to use in generated PDF files.

     * If $CFG->pdfexportfont is set - use it, otherwise use "freesans" as this

     * open licensed font has wide support for different language charsets.

     *

     * @return string

     */

    private function get_export_font_name() {

        $fontname = 'freesans';

        if (!empty($this->fontname)) {

            $fontname = $this->fontname;

        }

        return $fontname;

    }

    /**

     * Set font name.

     *

     * @param string $fontname Font name which is

     * @return void

     */

    public function set_export_font_name($fontname): void {

        $this->fontname = $fontname;

    }

    /**

     * Combine the given PDF files into a single PDF. Optionally add a coversheet and coversheet fields.

     * @param string[] $pdflist  the filenames of the files to combine

     * @param string $outfilename the filename to write to

     * @return int the number of pages in the combined PDF

     */

    public function combine_pdfs($pdflist, $outfilename) {

        raise_memory_limit(MEMORY_EXTRA);

        $olddebug = error_reporting(0);

        $this->setPageUnit('pt');

        $this->setPrintHeader(false);

        $this->setPrintFooter(false);

        $this->scale = 72.0 / 100.0;

        // Use font supporting the widest range of characters.

        $this->SetFont($this->get_export_font_name(), '', 16.0 * $this->scale, '', true);

        $this->SetTextColor(0, 0, 0);

        $totalpagecount = 0;

        foreach ($pdflist as $file) {

            $pagecount = $this->setSourceFile($file);

            $totalpagecount += $pagecount;

            for ($i = 1; $i<=$pagecount; $i++) {

                $this->create_page_from_source($i);

            }

        }

        $this->save_pdf($outfilename);

        error_reporting($olddebug);

        return $totalpagecount;

    }

    /**

     * The number of the current page in the PDF being processed

     * @return int

     */

    public function current_page() {

        return $this->currentpage;

    }

    /**

     * The total number of pages in the PDF being processed

     * @return int

     */

    public function page_count() {

        return $this->pagecount;

    }

    /**

     * Load the specified PDF and set the initial output configuration

     * Used when processing comments and outputting a new PDF

     * @param string $filename the path to the PDF to load

     * @return int the number of pages in the PDF

     */

    public function load_pdf($filename) {

        raise_memory_limit(MEMORY_EXTRA);

        $olddebug = error_reporting(0);

        $this->setPageUnit('pt');

        $this->scale = 72.0 / 100.0;

        $this->SetFont($this->get_export_font_name(), '', 16.0 * $this->scale, '', true);

        $this->SetFillColor(255, 255, 176);

        $this->SetDrawColor(0, 0, 0);

        $this->SetLineWidth(1.0 * $this->scale);

        $this->SetTextColor(0, 0, 0);

        $this->setPrintHeader(false);

        $this->setPrintFooter(false);

        $this->pagecount = $this->setSourceFile($filename);

        $this->filename = $filename;

        error_reporting($olddebug);

        return $this->pagecount;

    }

    /**

     * Sets the name of the PDF to process, but only loads the file if the

     * pagecount is zero (in order to count the number of pages)

     * Used when generating page images (but not a new PDF)

     * @param string $filename the path to the PDF to process

     * @param int $pagecount optional the number of pages in the PDF, if known

     * @return int the number of pages in the PDF

     */

    public function set_pdf($filename, $pagecount = 0) {

        if ($pagecount == 0) {

            return $this->load_pdf($filename);

        } else {

            $this->filename = $filename;

            $this->pagecount = $pagecount;

            return $pagecount;

        }

    }

    /**

     * Copy the next page from the source file and set it as the current page

     * @return bool true if successful

     */

    public function copy_page() {

        if (!$this->filename) {

            return false;

        }

        if ($this->currentpage>=$this->pagecount) {

            return false;

        }

        $this->currentpage++;

        $this->create_page_from_source($this->currentpage);

        return true;

    }

    /**

     * Create a page from a source PDF.

     *

     * @param int $pageno

     */

    protected function create_page_from_source($pageno) {

        // Get the size (and deduce the orientation) of the next page.

        $template = $this->importPage($pageno);

        $size = $this->getTemplateSize($template);

        // Create a page of the required size / orientation.

        $this->AddPage($size['orientation'], array($size['width'], $size['height']));

        // Prevent new page creation when comments are at the bottom of a page.

        $this->setPageOrientation($size['orientation'], false, 0);

        // Fill in the page with the original contents from the student.

        $this->useTemplate($template);

    }

    /**

     * Copy all the remaining pages in the file

     */

    public function copy_remaining_pages() {

        $morepages = true;

        while ($morepages) {

            $morepages = $this->copy_page();

        }

    }

    /**

     * Append all comments to the end of the document.

     *

     * @param array $allcomments All comments, indexed by page number (starting at 0).

     * @return array|bool An array of links to comments, or false.

     */

    public function append_comments($allcomments) {

        if (!$this->filename) {

            return false;

        }

        $this->SetFontSize(12 * $this->scale);

        $this->SetMargins(100 * $this->scale, 120 * $this->scale, -1, true);

        $this->SetAutoPageBreak(true, 100 * $this->scale);

        $this->setHeaderFont(array($this->get_export_font_name(), '', 24 * $this->scale, '', true));

        $this->setHeaderMargin(24 * $this->scale);

        $this->setHeaderData('', 0, '', get_string('commentindex', 'assignfeedback_editpdf'));

        // Add a new page to the document with an appropriate header.

        $this->setPrintHeader(true);

        $this->AddPage();

        // Add the comments.

        $commentlinks = array();

        foreach ($allcomments as $pageno => $comments) {

            foreach ($comments as $index => $comment) {

                // Create a link to the current location, which will be added to the marker.

                $commentlink = $this->AddLink();

                $this->SetLink($commentlink, -1);

                $commentlinks[$pageno][$index] = $commentlink;

                // Also create a link back to the marker, which will be added here.

                $markerlink = $this->AddLink();

                $this->SetLink($markerlink, $comment->y * $this->scale, $pageno + 1);

                $label = get_string('commentlabel', 'assignfeedback_editpdf', array('pnum' => $pageno + 1, 'cnum' => $index + 1));

                $this->Cell(50 * $this->scale, 0, $label, 0, 0, '', false, $markerlink);

                $this->MultiCell(0, 0, $comment->rawtext, 0, 'L');

                $this->Ln(12 * $this->scale);

            }

            // Add an extra line break between pages.

            $this->Ln(12 * $this->scale);

        }

        return $commentlinks;

    }

    /**

     * Add a comment marker to the specified page.

     *

     * @param int $pageno The page number to add markers to (starting at 0).

     * @param int $index The comment index.

     * @param int $x The x-coordinate of the marker (in pixels).

     * @param int $y The y-coordinate of the marker (in pixels).

     * @param int $link The link identifier pointing to the full comment text.

     * @param string $colour The fill colour of the marker (red, yellow, green, blue, white, clear).

     * @return bool Success status.

     */

    public function add_comment_marker($pageno, $index, $x, $y, $link, $colour = 'yellow') {

        if (!$this->filename) {

            return false;

        }

        $fill = '';

        $fillopacity = 0.9;

        switch ($colour) {

            case 'red':

                $fill = 'rgb(249, 181, 179)';

                break;

            case 'green':

                $fill = 'rgb(214, 234, 178)';

                break;

            case 'blue':

                $fill = 'rgb(203, 217, 237)';

                break;

            case 'white':

                $fill = 'rgb(255, 255, 255)';

                break;

            case 'clear':

                $fillopacity = 0;

                break;

            default: /* Yellow */

                $fill = 'rgb(255, 236, 174)';

        }

        $marker = '@<svg xmlns="http://www.w3.org/2000/svg" viewBox="-0.5 -0.5 12 12" preserveAspectRatio="xMinYMin meet">' .

                '<path d="M11 0H1C.4 0 0 .4 0 1v6c0 .6.4 1 1 1h1v4l4-4h5c.6 0 1-.4 1-1V1c0-.6-.4-1-1-1z" fill="' . $fill . '" ' .

                'fill-opacity="' . $fillopacity . '" stroke="rgb(153, 153, 153)" stroke-width="0.5"/></svg>';

        $label = get_string('commentlabel', 'assignfeedback_editpdf', array('pnum' => $pageno + 1, 'cnum' => $index + 1));

        $x *= $this->scale;

        $y *= $this->scale;

        $size = 24 * $this->scale;

        $this->SetDrawColor(51, 51, 51);

        $this->SetFontSize(10 * $this->scale);

        $this->setPage($pageno + 1);

        // Add the marker image.

        $this->ImageSVG($marker, $x - 0.5, $y - 0.5, $size, $size, $link);

        // Add the label.

        $this->MultiCell($size * 0.95, 0, $label, 0, 'C', false, 1, $x, $y, true, 0, false, true, $size * 0.60, 'M', true);

        return true;

    }

    /**

     * Add a comment to the current page

     * @param string $text the text of the comment

     * @param int $x the x-coordinate of the comment (in pixels)

     * @param int $y the y-coordinate of the comment (in pixels)

     * @param int $width the width of the comment (in pixels)

     * @param string $colour optional the background colour of the comment (red, yellow, green, blue, white, clear)

     * @return bool true if successful (always)

     */

    public function add_comment($text, $x, $y, $width, $colour = 'yellow') {

        if (!$this->filename) {

            return false;

        }

        $this->SetDrawColor(51, 51, 51);

        switch ($colour) {

            case 'red':

                $this->SetFillColor(249, 181, 179);

                break;

            case 'green':

                $this->SetFillColor(214, 234, 178);

                break;

            case 'blue':

                $this->SetFillColor(203, 217, 237);

                break;

            case 'white':

                $this->SetFillColor(255, 255, 255);

                break;

            default: /* Yellow */

                $this->SetFillColor(255, 236, 174);

                break;

        }

        $x *= $this->scale;

        $y *= $this->scale;

        $width *= $this->scale;

        $text = str_replace('&lt;', '<', $text);

        $text = str_replace('>', '>', $text);

        // Draw the text with a border, but no background colour (using a background colour would cause the fill to

        // appear behind any existing content on the page, hence the extra filled rectangle drawn below).

        $this->MultiCell($width, 1.0, $text, 0, 'L', 0, 4, $x, $y); /* width, height, text, border, justify, fill, ln, x, y */

        if ($colour != 'clear') {

            $newy = $this->GetY();

            // Now we know the final size of the comment, draw a rectangle with the background colour.

            $this->Rect($x, $y, $width, $newy - $y, 'DF');

            // Re-draw the text over the top of the background rectangle.

            $this->MultiCell($width, 1.0, $text, 0, 'L', 0, 4, $x, $y); /* width, height, text, border, justify, fill, ln, x, y */

        }

        return true;

    }

    /**

     * Add an annotation to the current page

     * @param int $sx starting x-coordinate (in pixels)

     * @param int $sy starting y-coordinate (in pixels)

     * @param int $ex ending x-coordinate (in pixels)

     * @param int $ey ending y-coordinate (in pixels)

     * @param string $colour optional the colour of the annotation (red, yellow, green, blue, white, black)

     * @param string $type optional the type of annotation (line, oval, rectangle, highlight, pen, stamp)

     * @param int[]|string $path optional for 'pen' annotations this is an array of x and y coordinates for

     *              the line, for 'stamp' annotations it is the name of the stamp file (without the path)

     * @param string $imagefolder - Folder containing stamp images.

     * @return bool true if successful (always)

     */

    public function add_annotation($sx, $sy, $ex, $ey, $colour, $type, $path, $imagefolder) {

        global $CFG;

        if (!$this->filename) {

            return false;

        }

        switch ($colour) {

            case 'yellow':

                $colourarray = array(255, 207, 53);

                break;

            case 'green':

                $colourarray = array(153, 202, 62);

                break;

            case 'blue':

                $colourarray = array(125, 159, 211);

                break;

            case 'white':

                $colourarray = array(255, 255, 255);

                break;

            case 'black':

                $colourarray = array(51, 51, 51);

                break;

            default: /* Red */

                $colour = 'red';

                $colourarray = array(239, 69, 64);

                break;

        }

        $this->SetDrawColorArray($colourarray);

        $sx *= $this->scale;

        $sy *= $this->scale;

        $ex *= $this->scale;

        $ey *= $this->scale;

        $this->SetLineWidth(3.0 * $this->scale);

        switch ($type) {

            case 'oval':

                $rx = abs($sx - $ex) / 2;

                $ry = abs($sy - $ey) / 2;

                $sx = min($sx, $ex) + $rx;

                $sy = min($sy, $ey) + $ry;

                // $rx and $ry should be >= min width and height

                if ($rx < self::MIN_ANNOTATION_WIDTH) {

                    $rx = self::MIN_ANNOTATION_WIDTH;

                }

                if ($ry < self::MIN_ANNOTATION_HEIGHT) {

                    $ry = self::MIN_ANNOTATION_HEIGHT;

                }

                $this->Ellipse($sx, $sy, $rx, $ry);

                break;

            case 'rectangle':

                $w = abs($sx - $ex);

                $h = abs($sy - $ey);

                $sx = min($sx, $ex);

                $sy = min($sy, $ey);

                // Width or height should be >= min width and height

                if ($w < self::MIN_ANNOTATION_WIDTH) {

                    $w = self::MIN_ANNOTATION_WIDTH;

                }

                if ($h < self::MIN_ANNOTATION_HEIGHT) {

                    $h = self::MIN_ANNOTATION_HEIGHT;

                }

                $this->Rect($sx, $sy, $w, $h);

                break;

            case 'highlight':

                $w = abs($sx - $ex);

                $h = 8.0 * $this->scale;

                $sx = min($sx, $ex);

                $sy = min($sy, $ey) + ($h * 0.5);

                $this->SetAlpha(0.5, 'Normal', 0.5, 'Normal');

                $this->SetLineWidth(8.0 * $this->scale);

                // width should be >= min width

                if ($w < self::MIN_ANNOTATION_WIDTH) {

                    $w = self::MIN_ANNOTATION_WIDTH;

                }

                $this->Rect($sx, $sy, $w, $h);

                $this->SetAlpha(1.0, 'Normal', 1.0, 'Normal');

                break;

            case 'pen':

                if ($path) {

                    $scalepath = array();

                    $points = preg_split('/[,:]/', $path);

                    foreach ($points as $point) {

                        $scalepath[] = intval($point) * $this->scale;

                    }

                    if (!empty($scalepath)) {

                        $this->PolyLine($scalepath, 'S');

                    }

                }

                break;

            case 'stamp':

                $imgfile = $imagefolder . '/' . clean_filename($path);

                $w = abs($sx - $ex);

                $h = abs($sy - $ey);

                $sx = min($sx, $ex);

                $sy = min($sy, $ey);

                // Stamp is always more than 40px, so no need to check width/height.

                $this->Image($imgfile, $sx, $sy, $w, $h);

                break;

            default: // Line.

                $this->Line($sx, $sy, $ex, $ey);

                break;

        }

        $this->SetDrawColor(0, 0, 0);

        $this->SetLineWidth(1.0 * $this->scale);

        return true;

    }

    /**

     * Save the completed PDF to the given file

     * @param string $filename the filename for the PDF (including the full path)

     */

    public function save_pdf($filename) {

        $olddebug = error_reporting(0);

        $this->Output($filename, 'F');

        error_reporting($olddebug);

    }

    /**

     * Set the path to the folder in which to generate page image files

     * @param string $folder

     */

    public function set_image_folder($folder) {

        $this->imagefolder = $folder;

    }

    /**

     * Generate images from the PDF

     * @return array Array of filename of the generated images

     */

    public function get_images(): array {

        $this->precheck_generate_image();

        $imagefile = $this->imagefolder . '/' . self::IMAGE_PAGE;

        $command = $this->get_command_for_image(-1, $imagefile);

        exec($command);

        $images = array();

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

            // Image file is created from 1, so need to change to 0.

            $file = $imagefile . ($i + 1) . '.png';

            $newfile = $imagefile . $i . '.png';

            if (file_exists($file)) {

                rename($file, $newfile);

            } else {

                // Converter added '-' and zerofill for the pagenumber.

                $length = strlen($this->pagecount);

                $file = $imagefile . '-' . str_pad(($i + 1), $length, '0', STR_PAD_LEFT) . '.png';

                if (file_exists($file)) {

                    rename($file, $newfile);

                } else {

                    $newfile = self::get_error_image($this->imagefolder, $i);

                }

            }

            $images[$i] = basename($newfile);

        }

        return $images;

    }

    /**

     * Generate an image of the specified page in the PDF

     * @param int $pageno the page to generate the image of

     * @throws \moodle_exception

     * @throws \coding_exception

     * @return string the filename of the generated image

     */

    public function get_image($pageno) {

        $this->precheck_generate_image();

        $imagefile = $this->imagefolder . '/' . self::IMAGE_PAGE . $pageno . '.png';

        $generate = true;

        if (file_exists($imagefile)) {

            if (filemtime($imagefile) > filemtime($this->filename)) {

                // Make sure the image is newer than the PDF file.

                $generate = false;

            }

        }

        if ($generate) {

            $command = $this->get_command_for_image($pageno, $imagefile);

            $output = null;

            $result = exec($command, $output);

            if (!file_exists($imagefile)) {

                $fullerror = '<pre>'.get_string('command', 'assignfeedback_editpdf')."\n";

                $fullerror .= $command . "\n\n";

                $fullerror .= get_string('result', 'assignfeedback_editpdf')."\n";

                $fullerror .= htmlspecialchars($result, ENT_COMPAT) . "\n\n";

                $fullerror .= get_string('output', 'assignfeedback_editpdf')."\n";

                $fullerror .= htmlspecialchars(implode("\n", $output), ENT_COMPAT) . '</pre>';

                throw new \moodle_exception('errorgenerateimage', 'assignfeedback_editpdf', '', $fullerror);

            }

        }

        return self::IMAGE_PAGE . $pageno . '.png';

    }

    /**

     * Make sure the file name and image folder are ready before generate image.

     * @return bool

     */

    protected function precheck_generate_image() {

        if (!$this->filename) {

            throw new \coding_exception('Attempting to generate a page image without first setting the PDF filename');

        }

        if (!$this->imagefolder) {

            throw new \coding_exception('Attempting to generate a page image without first specifying the image output folder');

        }

        if (!is_dir($this->imagefolder)) {

            throw new \coding_exception('The specified image output folder is not a valid folder');

        }

        return true;

    }

    /**

     * Gets the command to use to extract as image the given $pageno page number

     * from a PDF document into the $imagefile file.

     * @param int $pageno Page number to extract from document. -1 means for all pages.

     * @param string $imagefile Target filename for the PNG image as absolute path.

     * @return string The command to use to extract a page as PNG image.

     */

    private function get_command_for_image(int $pageno, string $imagefile): string {

        global $CFG;

        // First, quickest convertion option.

        if (!empty($CFG->pathtopdftoppm) && is_executable($CFG->pathtopdftoppm)) {

            return $this->get_pdftoppm_command_for_image($pageno, $imagefile);

        }

        // Otherwise, rely on default behaviour.

        return $this->get_gs_command_for_image($pageno, $imagefile);

    }

    /**

     * Gets the pdftoppm command to use to extract as image the given $pageno page number

     * from a PDF document into the $imagefile file.

     * @param int $pageno Page number to extract from document. -1 means for all pages.

     * @param string $imagefile Target filename for the PNG image as absolute path.

     * @return string The pdftoppm command to use to extract a page as PNG image.

     */

    private function get_pdftoppm_command_for_image(int $pageno, string $imagefile): string {

        global $CFG;

        $pdftoppmexec = \escapeshellarg($CFG->pathtopdftoppm);

        $imageres = \escapeshellarg(100);

        $filename = \escapeshellarg($this->filename);

        $pagenoinc = \escapeshellarg($pageno + 1);

        if ($pageno >= 0) {

            // Convert 1 page.

            $imagefile = substr($imagefile, 0, -4); // Pdftoppm tool automatically adds extension file.

            $frompageno = $pagenoinc;

            $topageno = $pagenoinc;

            $singlefile = '-singlefile';

        } else {

            // Convert all pages at once.

            $frompageno = 1;

            $topageno = $this->pagecount;

            $singlefile = '';

        }

        $imagefilearg = \escapeshellarg($imagefile);

        return "$pdftoppmexec -q -r $imageres -f $frompageno -l $topageno -png $singlefile $filename $imagefilearg";

    }

    /**

     * Gets the ghostscript (gs) command to use to extract as image the given $pageno page number

     * from a PDF document into the $imagefile file.

     * @param int $pageno Page number to extract from document. -1 means for all pages.

     * @param string $imagefile Target filename for the PNG image as absolute path.

     * @return string The ghostscript (gs) command to use to extract a page as PNG image.

     */

    private function get_gs_command_for_image(int $pageno, string $imagefile): string {

        global $CFG;

        $gsexec = \escapeshellarg($CFG->pathtogs);

        $imageres = \escapeshellarg(100);

        $imagefilearg = \escapeshellarg($imagefile);

        $filename = \escapeshellarg($this->filename);

        $pagenoinc = \escapeshellarg($pageno + 1);

        if ($pageno >= 0) {

            // Convert 1 page.

            $firstpage = $pagenoinc;

            $lastpage = $pagenoinc;

        } else {

            // Convert all pages at once.

            $imagefilearg = \escapeshellarg($imagefile . '%d.png');

            $firstpage = 1;

            $lastpage = $this->pagecount;

        }

        return "$gsexec -q -sDEVICE=png16m -dSAFER -dBATCH -dNOPAUSE -r$imageres -dFirstPage=$firstpage -dLastPage=$lastpage ".

            "-dDOINTERPOLATE -dGraphicsAlphaBits=4 -dTextAlphaBits=4 -sOutputFile=$imagefilearg $filename";

    }

    /**

     * Check to see if PDF is version 1.4 (or below); if not: use ghostscript to convert it

     *

     * @param \stored_file $file

     * @return string path to copy or converted pdf (false == fail)

     */

    public static function ensure_pdf_compatible(\stored_file $file) {

        global $CFG;

        // Copy the stored_file to local disk for checking.

        $temparea = make_request_directory();

        $tempsrc = $temparea . "/source.pdf";

        $file->copy_content_to($tempsrc);

        return self::ensure_pdf_file_compatible($tempsrc);

    }

    /**

     * Flatten and convert file using ghostscript then load pdf.

     *

     * @param   string $tempsrc The path to the file on disk.

     * @return  string path to copy or converted pdf (false == fail)

     */

    public static function ensure_pdf_file_compatible($tempsrc) {

        global $CFG;

        $temparea = make_request_directory();

        $tempdst = $temparea . "/target.pdf";

        $gsexec = \escapeshellarg($CFG->pathtogs);

        $tempdstarg = \escapeshellarg($tempdst);

        $tempsrcarg = \escapeshellarg($tempsrc);

        $command = "$gsexec -q -sDEVICE=pdfwrite -dPreserveAnnots=false -dSAFER -dBATCH -dNOPAUSE "

            . "-sOutputFile=$tempdstarg $tempsrcarg";

        exec($command);

        if (!file_exists($tempdst)) {

            // Something has gone wrong in the conversion.

            return false;

        }

        $pdf = new pdf();

        $pagecount = 0;

        try {

            $pagecount = $pdf->load_pdf($tempdst);

        } catch (\Exception $e) {

            // PDF was not valid - try running it through ghostscript to clean it up.

            $pagecount = 0;

        }

        $pdf->Close(); // PDF loaded and never saved/outputted needs to be closed.

        if ($pagecount <= 0) {

            // Could not parse the converted pdf.

            return false;

        }

        return $tempdst;

    }

    /**

     * Generate an localised error image for the given pagenumber.

     *

     * @param string $errorimagefolder path of the folder where error image needs to be created.

     * @param int $pageno page number for which error image needs to be created.

     *

     * @return string File name

     * @throws \coding_exception

     */

    public static function get_error_image($errorimagefolder, $pageno) {

        global $CFG;

        $errorfile = $CFG->dirroot . self::BLANK_PDF;

        if (!file_exists($errorfile)) {

            throw new \coding_exception("Blank PDF not found", "File path" . $errorfile);

        }

        $tmperrorimagefolder = make_request_directory();

        $pdf = new pdf();

        $pdf->set_pdf($errorfile);

        $pdf->copy_page();

        $pdf->add_comment(get_string('errorpdfpage', 'assignfeedback_editpdf'), 250, 300, 200, "red");

        $generatedpdf = $tmperrorimagefolder . '/' . 'error.pdf';

        $pdf->save_pdf($generatedpdf);

        $pdf = new pdf();

        $pdf->set_pdf($generatedpdf);

        $pdf->set_image_folder($tmperrorimagefolder);

        $image = $pdf->get_image(0);

        $pdf->Close(); // PDF loaded and never saved/outputted needs to be closed.

        $newimg = self::IMAGE_PAGE . $pageno . '.png';

        copy($tmperrorimagefolder . '/' . $image, $errorimagefolder . '/' . $newimg);

        return $newimg;

    }

    /**

     * Test that the configured path to ghostscript is correct and working.

     * @param bool $generateimage - If true - a test image will be generated to verify the install.

     * @return \stdClass

     */

    public static function test_gs_path($generateimage = true) {

        global $CFG;

        $ret = (object)array(

            'status' => self::GSPATH_OK,

            'message' => null,

        );

        $gspath = $CFG->pathtogs;

        if (empty($gspath)) {

            $ret->status = self::GSPATH_EMPTY;

            return $ret;

        }

        if (!file_exists($gspath)) {

            $ret->status = self::GSPATH_DOESNOTEXIST;

            return $ret;

        }

        if (is_dir($gspath)) {

            $ret->status = self::GSPATH_ISDIR;

            return $ret;

        }

        if (!is_executable($gspath)) {

            $ret->status = self::GSPATH_NOTEXECUTABLE;

            return $ret;

        }

        if (!$generateimage) {

            return $ret;

        }

        $testfile = $CFG->dirroot.'/mod/assign/feedback/editpdf/tests/fixtures/testgs.pdf';

        if (!file_exists($testfile)) {

            $ret->status = self::GSPATH_NOTESTFILE;

            return $ret;

        }

        $testimagefolder = \make_temp_directory('assignfeedback_editpdf_test');

        $filepath = $testimagefolder . '/' . self::IMAGE_PAGE . '0.png';

        // Delete any previous test images, if they exist.

        if (file_exists($filepath)) {

            unlink($filepath);

        }

        $pdf = new pdf();

        $pdf->set_pdf($testfile);

        $pdf->set_image_folder($testimagefolder);

        try {

            $pdf->get_image(0);

        } catch (\moodle_exception $e) {

            $ret->status = self::GSPATH_ERROR;

            $ret->message = $e->getMessage();

        }

        $pdf->Close(); // PDF loaded and never saved/outputted needs to be closed.

        return $ret;

    }

    /**

     * If the test image has been generated correctly - send it direct to the browser.

     */

    public static function send_test_image() {

        global $CFG;

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

        require_once($CFG->libdir.'/filelib.php');

        $testimagefolder = \make_temp_directory('assignfeedback_editpdf_test');

        $testimage = $testimagefolder . '/' . self::IMAGE_PAGE . '0.png';

        send_file($testimage, basename($testimage), 0);

        die();

    }

    /**

     * This function add an image file to PDF page.

     * @param \stored_file $imagestoredfile Image file to be added

     */

    public function add_image_page($imagestoredfile) {

        $imageinfo = $imagestoredfile->get_imageinfo();

        $imagecontent = $imagestoredfile->get_content();

        $this->currentpage++;

        $template = $this->importPage($this->currentpage);

        $size = $this->getTemplateSize($template);

        $orientation = 'P';

        if ($imageinfo["width"] > $imageinfo["height"]) {

            if ($size['width'] < $size['height']) {

                $temp = $size['width'];

                $size['width'] = $size['height'];

                $size['height'] = $temp;

            }

            $orientation = 'L';

        } else if ($imageinfo["width"] < $imageinfo["height"]) {

            if ($size['width'] > $size['height']) {

                $temp = $size['width'];

                $size['width'] = $size['height'];

                $size['height'] = $temp;

            }

        }

        $this->SetHeaderMargin(0);

        $this->SetFooterMargin(0);

        $this->SetMargins(0, 0, 0, true);

        $this->setPrintFooter(false);

        $this->setPrintHeader(false);

        $this->AddPage($orientation, $size);

        $this->SetAutoPageBreak(false, 0);

        $this->Image('@' . $imagecontent, 0, 0, $size['width'], $size['height'],

            '', '', '', false, null, '', false, false, 0);

    }

}