title: Spring RestTemplate - I/O error reading PNG header
body: <p>I am making an API call to an external app (this app converts all images originally loaded into it to PNG).
  If the image was originally loaded into that app as a PNG then RestTemplate can get it fine. If it was originally loaded as something else then converted to PNG the below code throws an error when trying to get it using RestTemplate in Spring 4.1.1. The image displays fine on the external app. </p>
  
  <blockquote>
    <p>Caused by: javax.imageio.IIOException: I/O error reading PNG header!
        at com.sun.imageio.plugins.png.PNGImageReader.readHeader(PNGImageReader.java:315) ~[na:1.8.0_20]
        at com.sun.imageio.plugins.png.PNGImageReader.readMetadata(PNGImageReader.java:654) ~[na:1.8.0_20]
        at com.sun.imageio.plugins.png.PNGImageReader.readImage(PNGImageReader.java:1248) ~[na:1.8.0_20]
        at com.sun.imageio.plugins.png.PNGImageReader.read(PNGImageReader.java:1606) ~[na:1.8.0_20]
        at org.springframework.http.converter.BufferedImageHttpMessageConverter.read(BufferedImageHttpMessageConverter.java:174) ~[BufferedImageHttpMessageConverter.class:4.1.1.RELEASE]
        at org.springframework.http.converter.BufferedImageHttpMessageConverter.read(BufferedImageHttpMessageConverter.java:67) ~[BufferedImageHttpMessageConverter.class:4.1.1.RELEASE]
        at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:104) ~[HttpMessageConverterExtractor.class:4.1.1.RELEASE]
        at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:576) ~[RestTemplate.class:4.1.1.RELEASE]
        ... 74 common frames omitted
    Caused by: javax.imageio.IIOException: Bad PNG signature!
        at com.sun.imageio.plugins.png.PNGImageReader.readHeader(PNGImageReader.java:242) ~[na:1.8.0_20]</p>
  </blockquote>
  
  <pre><code>BufferedImage image = restTemplate.getForObject(getPhotoUrl(), BufferedImage.class, Collections.EMPTY_MAP);
  </code></pre>