Render Html as Image - html

Question

I have a page with a form and button called preview. I need a method to generate a preview, converting the generated HTML to an image.
Clicking on the preview button starts an ajax call to a controller action (I'm using Yii Framework), so I collected all the data from the form and generated a preview with the filled data.
I need to convert the generated HTML to an image; in this way I'm able to re-size to my needed dimension.
I've tried generating a .pdf on the fly and then generate the image from the pdf, and using mpdf extension and imagick. But imagick requires the pdf to be an existing file, while I prefer to generate a .pdf string with mpdf (I can't generate and delete a pdf for each click on preview button).
What is a good method to generate an image from html or from pdf string generated "on the fly"?
This is the code that I've used, but it return an error from imagick, saying image without dimension:
$html2pdf = Yii::app()->ePdf->mpdf('','A4');
$html2pdf->WriteHTML($this->render('preview', array("data" => $data, "imageProvider" => $arrayImage),true));
$content_PDF = $html2pdf->Output('', EYiiPdf::OUTPUT_TO_STRING);
$im = new Imagick();
$im->readImageBlob( $content_pdf );
//$im->setIteratorIndex(0);
$im->setResolution( 800, 600 );
$im->setImageFormat( "jpeg" );
header( "Content-Type: image/jpeg" );
echo $im->getImage();

Answer 1

You need to rethink the requirement to take HTML and generate an image file of it.
I need to convert the generated HTML to an image; in this way I'm able
to re-size to my needed dimension.
You can easily resize the dimension and all elements within a form using proper CSS. This is the route I would take.
Generating an image seems like overkill.

Answer 2

In order to use Imagick, you need to set the SIZE of the picture, not only the solutions:
Can you try something like this first and see what happens?
$thumb = new imagick("/path/".$filename);
$thumb->setImageFormat( "png" );
$thumb->thumbnailImage( 128, 128);