I got it by adding my image into a cell like below
require('lib/fpdf.php');
$image = MEDIA_DIR."uploads/pdf_images/".$report_img.".png";
list($width, $height, $type, $attr) = getimagesize($image);
$pdf = new FPDF();
$pdf->SetSize(($width/2)+110,($height*57/100)); //Custom function
$pdf->AddPage('','custom');
$pdf->cell(1000,1000,'',$pdf->Image($image,10,10,235,$height*18/100),'PNG');
$pdf->Output();
Add the below function to fpdf.php
function SetSize($width,$height)
{
$this->StdPageSizes['custom']=array($width,$height);
}
solved How to increase the paper size as per my image size using FPDF-php?