title: Python Wand Scaling Issue
body: <p>I'm using Python Wand module(version 0.4.3.) to convert an image stored in pdf to PNG. Final PNG quality is great when I saved the final image in its orignal image width and height. But, when I try to save it to smaller image final PNG gets blurry and quality is not that great.</p>
  
  <p>The difference between two images is shown <a href="https://www.dropbox.com/s/0fk9ftpkpb0qm65/Screenshot%202016-10-31%2021.46.20.png?dl=0" rel="nofollow noreferrer">here</a>. Top image is converted to original size (10800x7200px). The second one is scale to 1250x833px. </p>
  
  <p>Is there any way I can improve the  second image? I played with different filter and blur setting.But, could not get the image quality I want. Any help is greatly appreciated. </p>
  
  <p>Code I used to convert PDF to png in its original size:</p>
  
  <pre><code> def pdf_to_png(pdf_name, res):
        with Image(filename=pdf_name,  resolution=res) as img:
             with Image(width=img.width,height=img.height, background=Color("white")) as bg:
                  bg.composite(img,0,0)`
                  bg.save(filename="Drawing_improved_wand.png")`
   pdf_to_png('Drawing_1.pdf', 300)
  </code></pre>
  
  <p>Code for resized png:</p>
  
  <pre><code> with Image(filename="Drawing_1.pdf",  resolution=(300,300)) as img:
        with Image(width=1250, height=833, background=Color("white")) as bg:
             img.resize(1250, 833,filter='undefined', blur=1)
             img.format = 'png'
             bg.composite(img,0,0)
             bg.save(filename='Drawing_improved_wand1250x833.png')
  </code></pre>