cache resources exhausted Imagemagick

I'm using Imagemagick on a rails app with Minimagick and I generate some pictogram with it.

When I launch my process I have this error and I don't find a solution:

MiniMagick::Error (`convert -limit memory 2GiB -limit map 2GiB -limit   disk 4GiB -background none -fill #000000 -font ttf/SELIS006N.ttf -pointsize 300 label: S public/pictogram_images/RECINTAN-EL-064-layer-1.png` failed with error:
convert.im6: cache resources exhausted ` S' @ error/cache.c/OpenPixelCache/4078.
convert.im6: no images defined `public/pictogram_images/RECINTAN-EL-064-layer-1.png' @ error/convert.c/ConvertImageCommand/3044.
):

My process is simple, I have some .tff file and each character is a pictogram. I just want to generate all preview of this character in png.

Find the policy.xml with find / -name "policy.xml"

something like /etc/ImageMagick-6/policy.xml

and change <policy domain="resource" name="disk" value="1GiB"/> to <policy domain="resource" name="disk" value="8GiB"/>

refer to convert fails due to resource limits

Memory issues

The error probably occurs because you run out of memory. You can check for the resources using the following command:

convert -list resource

The output will be somewhat like this:

Resource limits:
  Width: 16KP   
  Height: 16KP   
  Area: 128MP   
  Memory: 256MiB   
  Map: 512MiB   
  Disk: 1GiB   
  File: 768   
  Thread: 8   
  Throttle: 0   
  Time: unlimited

Here, you can see that the assigned amounts of disk space and memory are very small. So, in order to modify it you need to change the policy.xml file located somewhere in /etc/ImageMagick-6 directory.
Change <policy domain="resource" name="disk" value="1GiB"/> to <policy domain="resource" name="disk" value="4GiB"/> in the policy.xml file.

sed -i '/disable ghostscript format types/,+6d' /etc/ImageMagick-6/policy.xml //this one is just to solve convertion from .tiff to pdf, you may need it some day
sed -i -E 's/name="memory" value=".+"/name="memory" value="8GiB"/g' /etc/ImageMagick-6/policy.xml
sed -i -E 's/name="map" value=".+"/name="map" value="8GiB"/g' /etc/ImageMagick-6/policy.xml
sed -i -E 's/name="area" value=".+"/name="area" value="8GiB"/g' /etc/ImageMagick-6/policy.xml
sed -i -E 's/name="disk" value=".+"/name="disk" value="8GiB"/g' /etc/ImageMagick-6/policy.xml