title: ImageMagick error with rails
body: <p>I use MiniMagick (A ruby wrapper for ImageMagick) with rails-4.2 (ruby 2.2.0) on a linux server. </p>
  
  <p>I generate images via ttf. Each image has from 1 to 10 layers I then merged to create an image. I get an error which I can not find the solution. </p>
  
  <pre><code>MiniMagick::Error (`convert -background none -fill #000000 -font ttf/SELIS006N.ttf -pointsize 300 label: S public/pictogram_images/873-layer-2.png` failed with error:
    convert.im6: invalid geometry `+3.35542e+07+300.5' @ error/geometry.c/ParsePageGeometry/1407.
    convert.im6: unable to clone cache `/tmp/magick-1r313oY0': No space left on device @ error/cache.c/CloneDiskToDiskPixelCache/852.
    convert.im6: Image width exceeds user limit in IHDR `public/pictogram_images/873-layer-2.png' @ warning/png.c/MagickPNGWarningHandler/1754.
    convert.im6: Invalid IHDR data `public/pictogram_images/873-layer-2.png' @ error/png.c/MagickPNGErrorHandler/1728.
  ):
  </code></pre>
  
  <p>SELIS006N.ttf is my ttf files, the character is "S" and the image path is public/pictogram_images/873-layer-2.png</p>
  
  <p>I test the character with the same .ttf character and it's a completely normal without particuliarity.</p>