Question

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.getWidth();
        //this.tstCon.remove(trueImage);
        //trueImage = null;
        GWT.log("Image [" + this.imgTitle + "] -> height=" + this.trueHeight + " -> width=" + this.trueWidth);//
    }

Answer 1

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.