I am working with fpdf to convert html to pdf . I have the following html in new.html .
I also faced the same problem much time then I started to read all code of FPDF. I got my solution by changing some line fpdf.php. FPDF.php is core file in FPDF Library. So keep backup of this file before any change.
In this file I just searched
Not a JPEG file
then i comment out this line and set a default value
//$this->Error('Not a JPEG file: '.$file);
$colspace ="DeviceRGB";
After this, my PDF going generate. Note that in my case Image path was valid and i was upload image on S3 using base64 Decode also Croping too. so that maybe my image going working wrong. but it was being open on the browser. So after two change on fpdf.php. I got my solution.
Another thing you have to check is the image path is valid or not. in pdf file i am using
$pdf->Image($file,12,12,30,30);