How to increase quality of image through imagemagick binary convert?

Question

I'm working in an image conversion using imageMagick binary convert. When i resize a small image into a larger image and also increase the quality of image.
Here's my sample code:

$img = 'old_image.png';
$path1= 'new_img.png';
exec("convert $img -quality 100% -density 600  -resize 2480x3508 -depth 400 $path1");

When i used this command its working fine and it convert large image with loss of quality.
When i need to increase quality by using sharpen 50% code in exec command it doesn't create a proper image and no response in exec command.

$img = 'old_image.png';
$path1= 'new_img.png';
exec("convert $img -sharpen 99% -quality 100% -density 600  -resize 2480x3508 -depth 400 $path1");

Here I'm using image magick binary convert. How to achieve this image quality. Any help would be appreciated.

Answer 1

Think sharpen works like blur and takes an argument of {radius}x{sigma}

What version are you using? Maybe look at some of the docs that correspond to it...

http://www.imagemagick.org/Usage/blur