Another update from ingydotnet^djgoku

Task/Grayscale-image/Julia/grayscale-image-1.julia

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+using Color, Images, FixedPointNumbers
+
+const M_RGB_Y = reshape(Color.M_RGB_XYZ[2,:], 3)
+
+function rgb2gray(img::Image)
+    g = red(img)*M_RGB_Y[1] + green(img)*M_RGB_Y[2] + blue(img)*M_RGB_Y[3]
+    g = clamp(g, 0.0, 1.0)
+    return grayim(g)
+end
+
+function gray2rgb(img::Image)
+    colorspace(img) == "Gray" || return img
+    g = map((x)->RGB{Ufixed8}(x, x, x), img.data)
+    return Image(g, spatialorder=spatialorder(img))
+end
+
+ima = imread("grayscale_image_color.png")
+imb = rgb2gray(ima)
+imc = gray2rgb(imb)
+imwrite(imc, "grayscale_image_rc.png")

Task/Grayscale-image/Julia/grayscale-image-2.julia

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+using Color, Images, FixedPointNumbers
+
+ima = imread("grayscale_image_color.png")
+imb = convert(Image{Gray{Ufixed8}}, ima)
+imwrite(imb, "grayscale_image_julia.png")