hello, are the coordinates for the method getColorAt relative? and checks it only colors of the image or the other things too?
erdelf wrote ...
2012/5/31
getColorAt(int x, int y), coordinates relative?
You can 'getBackground().getColorAt(x, y)' for the world class image; and you can 'getImage().getColorAt(x, y)' for an actor image (you can even 'GreenfootImage("imageName").getColorAt(x, y)' for an image that is not currently displayed). Either way the x and y are relative to the top-left corner of the image (which is (0, 0)), and you can use the 'getColorAt(x, y)' on any GreenfootImage object.
Is there a way to check the color on specific coordinates, independent from objects on this position, but if there is one, the color of the object should be checked?
Use the 'getWorld().getObjectsAt(x, y, null)' (if not in the world class) to get a list of the objects that intersect that point. Somehow you will have to figure out which object is on top (it should not be too hard to figure out the class of object on top; that is, if you have used the 'setPaintOrder' command in the world constructor. However, if more that one object of the same class is at that point, the only solution I can think of right now, is to add a Long 'timeAddedToWorld' instance variable to all the actor classes along with a 'addedToWorld(World world) method to set the variable to System time; and use that variable to determine which one will be on top of the others (the one that was added to the world last). From there you would figure out what point in its image is at the location in question and get its color.
hm, maybe. Is there a way I can convert the relative coordinates to coordinates of the world?
Use getX() and getY(). If 'a' is the actor:
Remember, if the actor is close to an edge, the values above could end up outside the world bounds.
int realLeft = a.getX() - a.getImage().getWidth() / 2; int realTop = a.getY() - a.getImage().getHeight() / 2;
To convert world coordinates to the specific coordinates of the image of an actor:
int realX = whatever; int realY = whatever; Actor a = getObjectAt(realX, realY, null); int imageX = realX - a.getX() + a.getImage().getWidth() / 2; int imageY = realY - a.getY() + a.getImage().getHeight() / 2;
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