opencl implementation of canny edge algorithm on java.awt.image.BufferedImage

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I need some help understanding the opencl implementation for the canny edge detection algorithm.

I'm trying to compile and run this with jocl, with a java.awt.image.BufferedImage and I've succeeded in getting the kernals compiling. However, when I pass in the array into the kernal, I get no output and the output of the first stage looks like this:

Please let me know what I'm doing wrong and what else I may be able to do.

The source code looks something like this. I followed the compilation process for canny.cpp and canny.cl

(def canny-stage1 (kernel/load-executive
                   {:name "stage1_with_sobel"
                    :file "opencl/canny.cl"
                    :options "-D WITH_SOBEL -D cn=1 -D TYPE=uchar -D convert_floatN=convert_float -D floatN=float -D GRP_SIZEX=32 -D GRP_SIZEY=8 -D L2GRAD"
                    :worksize (fn [src _ _ _ _ map _ _ _ _]
                                [(.getWidth  src)
                                 (.getHeight src)])
                    :arglist [{:type :image
                               :name :src
                               :buffer {:input true}
                               :flags [:read-only]}
                              {:type :int
                               :name :src-step}
                              {:type :int
                               :name :src-offset}
                              {:type :int
                               :name :rows}
                              {:type :int
                               :name :cols}
                              {:type :image
                               :name :map
                               :buffer {:output true}
                               :flags [:write-only]}
                              {:type :int
                               :name :map-step}
                              {:type :int
                               :name :map-offset}
                              {:type :float
                               :name :low-threshold}
                              {:type :float
                               :name :high-threshold}]}))

(def input (javax.imageio.ImageIO/read (io/file "lena-1000x1000.jpg"))

(def buffer (BufferedImage. (.getWidth input)
                               (.getHeight input)
                               BufferedImage/TYPE_BYTE_GRAY))

(let [offset 0
        step (.getWidth input)
        rows (.getHeight input)
        cols (.getWidth input)]
    (canny-stage1 input
                  step
                  offset
                  rows
                  cols
                  buffer
                  step
                  offset
                  low-threshold
                  high-threshold))

(display-image buffer)