pChart image render issue on prod server and same script is working on dev server, while configurations are same

Question

I am having the issue with pChart image rendering, The chart image is not displaying on screen on my production server while the same script is working fine on development server.

Even,I have checked and compared configuration of both servers its are almost same. In only one scenario, The image is display with same script on production server, when i restart my prod server but after some times it not work automatically. I don't know what is the root cause of it.

Please help to solve this issue. Below is the screenshot of code:

<?php   
/* CAT:Area Chart */

/* pChart library inclusions */
include("../class/pData.class.php");
include("../class/pDraw.class.php");
include("../class/pImage.class.php");

/* Create and populate the pData object */
$MyData = new pData();  

for($i=0;$i<=30;$i++) { $MyData->addPoints(rand(1,15),"Probe 1"); }
$MyData->setSerieTicks("Probe 2",4);
$MyData->setAxisName(0,"Temperatures");

/* Create the pChart object */
$myPicture = new pImage(700,230,$MyData);

/* Turn of Antialiasing */
$myPicture->Antialias = FALSE;

/* Add a border to the picture */
$myPicture->drawGradientArea(0,0,700,230,DIRECTION_VERTICAL,array("StartR"=>240,"StartG"=>240,"StartB"=>240,"EndR"=>180,"EndG"=>180,"EndB"=>180,"Alpha"=>100));
$myPicture->drawGradientArea(0,0,700,230,DIRECTION_HORIZONTAL,array("StartR"=>240,"StartG"=>240,"StartB"=>240,"EndR"=>180,"EndG"=>180,"EndB"=>180,"Alpha"=>20));

/* Add a border to the picture */
$myPicture->drawRectangle(0,0,699,229,array("R"=>0,"G"=>0,"B"=>0));

/* Write the chart title */ 
$myPicture->setFontProperties(array("FontName"=>"../fonts/Forgotte.ttf","FontSize"=>11));
$myPicture->drawText(150,35,"Average temperature",array("FontSize"=>20,"Align"=>TEXT_ALIGN_BOTTOMMIDDLE));

/* Set the default font */
$myPicture->setFontProperties(array("FontName"=>"../fonts/pf_arma_five.ttf","FontSize"=>6));

/* Define the chart area */
$myPicture->setGraphArea(60,40,650,200);

/* Draw the scale */
$scaleSettings = array("XMargin"=>10,"YMargin"=>10,"Floating"=>TRUE,"GridR"=>200,"GridG"=>200,"GridB"=>200,"GridAlpha"=>100,"DrawSubTicks"=>TRUE,"CycleBackground"=>TRUE);
$myPicture->drawScale($scaleSettings);

/* Write the chart legend */
$myPicture->drawLegend(640,20,array("Style"=>LEGEND_NOBORDER,"Mode"=>LEGEND_HORIZONTAL));

/* Turn on Antialiasing */
$myPicture->Antialias = TRUE;

/* Enable shadow computing */
$myPicture->setShadow(TRUE,array("X"=>1,"Y"=>1,"R"=>0,"G"=>0,"B"=>0,"Alpha"=>10));

/* Draw the area chart */
$Threshold = "";
$Threshold[] = array("Min"=>0,"Max"=>5,"R"=>187,"G"=>220,"B"=>0,"Alpha"=>100);
$Threshold[] = array("Min"=>5,"Max"=>10,"R"=>240,"G"=>132,"B"=>20,"Alpha"=>100);
$Threshold[] = array("Min"=>10,"Max"=>20,"R"=>240,"G"=>91,"B"=>20,"Alpha"=>100);
$myPicture->setShadow(TRUE,array("X"=>1,"Y"=>1,"R"=>0,"G"=>0,"B"=>0,"Alpha"=>20));
$myPicture->drawAreaChart(array("Threshold"=>$Threshold));

/* Draw a line chart over */
$myPicture->drawLineChart(array("ForceColor"=>TRUE,"ForceR"=>0,"ForceG"=>0,"ForceB"=>0));

/* Draw a plot chart over */
$myPicture->drawPlotChart(array("PlotBorder"=>TRUE,"BorderSize"=>1,"Surrounding"=>-255,"BorderAlpha"=>80));

/* Write the thresholds */
$myPicture->drawThreshold(5,array("WriteCaption"=>TRUE,"Caption"=>"Warn Zone","Alpha"=>70,"Ticks"=>2,"R"=>0,"G"=>0,"B"=>255));
$myPicture->drawThreshold(10,array("WriteCaption"=>TRUE,"Caption"=>"Error Zone","Alpha"=>70,"Ticks"=>2,"R"=>0,"G"=>0,"B"=>255));

/* Render the picture (choose the best way) */
//$myPicture->autoOutput("pictures/example.drawAreaChart.threshold.png");
$myPicture->stroke();
?>

Not displaying image like below screenshot:

Answer 1

This issue has been resolved after deep investigation. I have replaced imagepng() to imagejpeg() in class/pImage.class.php. I replaced imagepng() to imagejpeg() function at 2 places below are description given:

1) In render function

function render($FileName)
    {
     if ( $this->TransparentBackground ) { imagealphablending($this->Picture,false); imagesavealpha($this->Picture,true); }
     imagejpeg($this->Picture,$FileName);
    }

2) In stroke function

 function stroke($BrowserExpire=FALSE)
    {
     if ( $this->TransparentBackground ) { imagealphablending($this->Picture,false); imagesavealpha($this->Picture,true); }

     if ( $BrowserExpire )
      {
       header("Expires: Mon, 26 Jul 1997 05:00:00 GMT");
       header("Cache-Control: no-cache");
       header("Pragma: no-cache");
      }

     header('Content-type: image/png');
     imagejpeg($this->Picture);
    }