Data commit

Task/Grayscale-image/R/grayscale-image.r

@@ -0,0 +1,33 @@
+# Conversion from Grey to RGB uses the following code
+setAs("pixmapGrey", "pixmapRGB",
+function(from, to){
+    z = new(to, as(from, "pixmap"))
+    z@red = from@grey
+    z@green = from@grey
+    z@blue = from@grey
+    z@channels = c("red", "green", "blue")
+    z
+})
+
+# Conversion from RGB to grey uses built-in coefficients of 0.3, 0.59, 0.11.  To see this, type
+getMethods(addChannels)
+
+# We can override this behaviour with
+setMethod("addChannels", "pixmapRGB",
+function(object, coef=NULL){
+    if(is.null(coef)) coef = c(0.2126, 0.7152, 0.0722)
+    z = new("pixmapGrey", object)
+    z@grey = coef[1] * object@red + coef[2] * object@green +
+        coef[3] * object@blue
+    z@channels = "grey"
+    z
+})
+
+# Colour image
+plot(p1 <- pixmapRGB(c(c(1,0,0,0,0,1), c(0,1,0,0,1,0), c(0,0,1,1,0,0)), nrow=6, ncol=6))
+
+#Convert to grey
+plot(p2 <- as(p1, "pixmapGrey"))
+
+# Convert back to "colour"
+plot(p3 <- as(p2, "pixmapRGB"))