add loadPixels() to mask() as well

core/src/processing/core/PImage.java

@@ -352,10 +352,9 @@ public class PImage implements PConstants, Cloneable {
     int index = y*width + x;
     int index2 = 0;
     for (int row = y; row < y+h; row++) {
-      System.arraycopy(pixels, index,
-                       newbie.pixels, index2, w);
-      index+=width;
-      index2+=w;
+      System.arraycopy(pixels, index, newbie.pixels, index2, w);
+      index += width;
+      index2 += w;
     }
     return newbie;
   }
@@ -455,6 +454,7 @@ public class PImage implements PConstants, Cloneable {
    * performing a proper luminance-based conversion.
    */
   public void mask(int alpha[]) {
+    loadPixels();
     // don't execute if mask image is different size
     if (alpha.length != pixels.length) {
       throw new RuntimeException("The PImage used with mask() must be " +

core/todo.txt

@@ -23,6 +23,9 @@ _   undo this--may need to be better about specifying screen and all
 X PImage mask doesn't work after first call
 X   http://dev.processing.org/bugs/show_bug.cgi?id=744
 
+_ work through loadPixels in PImage, how consistent do we need to be?
+_   with get() and set() methods, this gets really tricky (too slow)
+
 _ change openStream() to createInput()
 _   add createOutput() (and raw versions of the same, err.. no raw)
 _   deprecate openStream() naming