I have no background with Java so I tend to suffer pain when dealing with
it. I am trying to create a thumbnail for an image, but my code dies on the
:post assertion of this function:
(defn get-file-as-image [filename]
{:pre [(= (type filename) java.lang.String)
(fs/exists? filename)
(fs/file? (io/as-file filename))]
:post [(do (pp/pprint %) true)
(= (type %) BufferedImage)]}
(javax.imageio.ImageIO/read (io/as-file filename)))
"fs" refers to:
https://github.com/Raynes/fs/blob/master/src/me/raynes/fs.clj
The :pre assertions are all apparently true, so the file exists and returns
as a file when run through (io/as-file).
I looked here for the documentation on javax.imageio.ImageIO/read:
http://docs.oracle.com/javase/7/docs/api/javax/imageio/ImageIO.html#read(java.io.File)
It reads:
"Returns a BufferedImage as the result of decoding a supplied File with an
ImageReader chosen automatically from among those currently registered. The
File is wrapped in an ImageInputStream. If no registeredImageReader claims
to be able to read the resulting stream, null is returned."
I added the pprint into my :post and it prints nil. So I assume the problem
is this:
"If no registeredImageReader claims to be able to read the resulting
stream, null is returned."
What does it mean to register an ImageReader?
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