Gwt Image original size

I use an Image object to load a png image as a thumbnail by calling its setPixelSize() method to resize the image. I also need to retrieve the original size of the image as integers at some point. How can I get the original sizes (width, height) of the image?

ok i found a workaround: I use a dummy container (SimplePanel) and load the image without scaling save its real dimensions and then remove the container from the parent and discard the new Image object. I don't know if this a good workaround, but it works. Although i would like to know if there is another way...

problem of the workaround: I have a droplist from which i can select logical folders (which contain images). When i select a new folder, and the new set of images is loaded on display, then i get 0 for width and 0 for height.

private void getTrueSize(String fullUrl) {
        Image trueImage = new Image();
        this.tstCon.add(trueImage);
        trueImage.setUrl(fullUrl);
        this.trueHeight = trueImage.getHeight();
        this.trueWidth = trueImage.开发者_JAVA技巧getWidth();
        //this.tstCon.remove(trueImage);
        //trueImage = null;
        GWT.log("Image [" + this.imgTitle + "] -> height=" + this.trueHeight + " -> width=" + this.trueWidth);//
    }

Extend the Image class and implement onAttach() method. This method is called when a widget is attached to the browser's document.

public class Thumb extends Image {

    public Thumb(){
        super();
    }

    protected void onAttach(){
        Window.alert(getOffsetHeight()+" "+getOffsetWidth()); //this should give you the original value
        setPixelSize(10,10); // this should be the visible value 
        super.onAttach();
    }
}

if this doesn't work, try implementing onLoad() instead of onAttach(), since onLoad() will be called after the image is added to DOM so that it definately should work.

Its the easiest way to create a new hidden Image (placed absolute outside the viewport) and read the size. There is a JavaScript lib that can read the exif data of the image but this would be overkill in this case.

Read naturalHeight and naturalWidth of the image element after image load.

    public Panel() {
        image = new Image();
        image.addLoadHandler(this::onLoad);
    }

    private void onLoad(@SuppressWarnings("unused") LoadEvent event) {
        origImageWidth = getNaturalWidth(image);
        origImageHeight = getNaturalHeight(image);
    }

    private static int getNaturalHeight(Image img) {
        return img.getElement().getPropertyInt("naturalHeight"); //$NON-NLS-1$
    }

    private static int getNaturalWidth(Image img) {
        return img.getElement().getPropertyInt("naturalWidth"); //$NON-NLS-1$
    }