set density parameter for imagick with php

Question

I want to convert a pdf page to a png image with Imagick.

I tried with PHP, but the image quality was very low.
When I tried with command line, the result was perfect.

PHP code

$im = new imagick( __DIR__ . DIRECTORY_SEPARATOR.$PDFName.'['.$i.']' );  
$params = $im->identifyImage();
$width = $params['geometry']['width']*1;
$height = $params['geometry']['height']*1;
$im->setResolution(400,400);
$im->resizeImage($width ,$height, imagick::FILTER_SINC, 1, true);
$im->writeImage(__DIR__ . DIRECTORY_SEPARATOR.'pdf_pages\\'.$i.'.png'); 
$im->clear(); 
$im->destroy();

Command line code

convert -density 400 a.pdf -resize 25% -a.png

PHP code (2nd attempt)

$im = new imagick( __DIR__ . DIRECTORY_SEPARATOR.$PDFName.'['.$i.']' );  
$im->setOption('density','400x400');
$im->setOption('resize','25%');
$im->writeImage(__DIR__ . DIRECTORY_SEPARATOR.'pdf_pages\\'.$i.'.png'); 
$im->clear(); 
$im->destroy();

Still bad results.

What can I do? I want to use the density parameter in my PHP code, but how?

Output with PHP

Output with command line

Answer 1

You need to set Resolution before you read the file.

$im = new imagick();
$im->setResolution(200,200);
$im->readImage(__DIR__ . DIRECTORY_SEPARATOR.$PDFName.'['.$i.']');

Than, the result will be perfect.

Hope this help someone.

Answer 2

From the manual http://php.net/manual/en/imagick.setresolution.php

Imagick::setResolution() must be called before loading or creating an image.

See this answer Pdf to image using php-imagick api