getScaledInstance java图像后的高度和宽度-1

Question

so for the wanky title. Didn't came up with a short pregnant description.

My problem are these lines of code:

ii = new ImageIcon("images/player.png");
image = ii.getImage();
image = image.getScaledInstance(SCALED_X, SCLAED_Y, Image.SCALE_SMOOTH);
positionX = windowWidth / 2 - image.getWidth() / 2; 
positionY = windowHeight - image.getHeight();

When I debugged the code I noticed that the image has a height and width of -1, after calling the getScaledInstance function, and therefore the last two lines return wrong results. A workaround I came up with is using SCALED_X and SCALED_Y as the new height and width but thats not that pretty -.- Can anybody explain why this is, ie the height and width have the value -1? Are these properties lost when using the getScaledInstance function (could not find any words about that in the documentation)? And is there any way to add them to the Image again?

Is there a way to reduce the size of an image and keep resp. automatically adjust the properties?

EDIT:

Changed code to get the Image to:

try {
    image = ImageIO.read(new File("images/player.png")).getScaledInstance(SCALED_X, SCLAED_Y, Image.SCALE_SMOOTH);          
} catch (IOException e) {
    e.printStackTrace();
}

Error with -1 still persists :(

Answer 1

Reading the Javadocs of the methods used suggests that the image has not been scaled yet when you call getHeight/getWidth:

getScaledInstance():

Creates a scaled version of this image. A new Image object is returned which will render the image at the specified width and height by default. The new Image object may be loaded asynchronously even if the original source image has already been loaded completely.

getHeight():

Determines the height of the image. If the height is not yet known, this method returns -1

You have several options: You can wait for the image to be scaled, or use an ImageObserver to calculate the required values when the width and height become available, or use your SCALED_X/Y constants instead of image.getWidth/Height, or scale the image yourself by creating a new BufferedImage and painting the old image onto the new one.

Another possibility is to simply assume that the player image is of the correct size - this will make your game load faster and the player will appear in-game exactly as it was drawn by the artist.