Grayscale image: Difference between revisions

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 =={{header|Clojure|Clojure}}==
 <lang clojure>
+(import '[java.io File]
-(ns rgb-to-gray.clj
+        '[javax.imageio ImageIO]
-  (:import [java.io File]
-           [javax.imageio ImageIO]
+        '[java.awt Color]
-           [java.awt Color]
+        '[java.awt.image BufferedImage]))
-           [java.awt.image BufferedImage]))
+(defn rgb-to-gray [color-image]
+  (let [width (.getWidth color-image)]
+    (partition width
+               (for [x (range width)
+                     y (range (.getHeight color-image))]
+                 (let [rgb (.getRGB color-image x y)
+                       rgb-object (new Color rgb)
+                       r (.getRed rgb-object)
+                       g (.getGreen rgb-object)
+                       b (.getBlue rgb-object)
+                       a (.getAlpha rgb-object)]
+                   ;Compute the grayscale value an return it: L = 0.2126·R + 0.7152·G + 0.0722·B
+                   (+ (* r 0.2126) (* g 0.7152) (* b 0.0722)))))))
-(defn rgb-to-gray [color-image] (map
-                  (fn [y] (
-                            map
-                            (
-                              fn [x]
-                              (
-                                let [rgb (.getRGB color-image x y) rgb-object (new Color rgb) ]
-                                  (
-                                  let [r (.getRed rgb-object) g (.getGreen rgb-object) b (.getBlue rgb-object) a (.getAlpha rgb-object)]
-                                  (
-                                    ;Compute the grayscale value an return it: L = 0.2126·R + 0.7152·G + 0.0722·B
-                                    + (* r 0.2126) (* g 0.7152) (* b 0.0722)
-                                    )
-                                   )
-                                  )
-                              )
-                            (
-                              range
-                              (
-                                .getWidth color-image
-                                )
-                              )
-                            )
-                    )
-                    (
-                      range
-                      (
-                        .getHeight color-image
-                        )
-                      )
-                  )
-  )
 (defn write-matrix-to-image [matrix filename]
+  (ImageIO/write
-  (ImageIO/write (let [height (count matrix) width (count (first matrix)) output-image (new BufferedImage width height BufferedImage/TYPE_BYTE_GRAY)]
+   (let [height (count matrix)
-                   (
-                     do
+         width (count (first matrix))
+         output-image (new BufferedImage width height BufferedImage/TYPE_BYTE_GRAY)]
-                     (spit "/dev/null" ( ;This is the only way I could find to force evaluation so that side-effects are applied. spit just writes to null file
+     (doseq [row-index    (range height)
-                              map
-                              (
+             column-index (range width)]
+       (.setRGB output-image column-index row-index (.intValue (nth (nth matrix row-index) column-index))))
-                                fn [row-index] (
+     output-image)
+   "png"
+   (new File filename)))
-                                  map (fn [column-index]
-                                             (
-                                               .setRGB output-image column-index row-index (.intValue (nth (nth matrix row-index) column-index))
-                                               )
-                                             )
-                                      (range width)
-                                   )
-                                )
-                              (range height)
-                              )
-                       )
-                   output-image
-                    )
-                   )
-    "png" (new File filename))
-  )
 (println
   (write-matrix-to-image
     (rgb-to-gray
-      (ImageIO/read (new File "test.jpg"))
+      (ImageIO/read (new File "test.jpg")))
+    "test-gray-cloj.png"))
-      )
-    "test-gray-cloj.png")
-  )
 </lang>