GWT Canvas - Save image and open it - html

Question

I save an image in a String, then when I open it it's always 300x150
Why is the image truncated?
Where does 300x150 come from?
The code is what you see. Just 2 buttons.
The first one saves the image in "png", and the other reads the image from "png"
Button save = new Button("copy");
save.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
ImageElement imageElement = ImageElement.as(image.getElement());
Canvas canvasTmp = Canvas.createIfSupported();
Context2d context = canvasTmp.getContext2d();
context.drawImage(imageElement, 0.0, 0.0, imageElement.getWidth(), imageElement.getHeight());
png = canvasTmp.toDataUrl("image/png");
}
});
Button open = new Button("open");
open.addClickHandler(new ClickHandler() {
#Override
public void onClick(ClickEvent event) {
final Image image = new Image(png);
vp.add(image);
image.addLoadHandler(new LoadHandler() {
#Override
public void onLoad(LoadEvent event)
{
Window.alert("ok");
}
});
image.addErrorHandler(new ErrorHandler() {
#Override
public void onError(ErrorEvent event) {
Window.alert("error");
}
} );
}
});

Answer 1

The canvas has a default width of 300 pixels and a default height of 150 pixels. After creating the canvas and before drawing the image, consider doing this:
int width = imageElement.getWidth()
int height = imageElement.getHeight()
canvasTmp.setWidth(width + "px");
canvasTmp.setHeight(height + "px");
canvasTmp.setCoordinateSpaceWidth(width);
canvasTmp.setCoordinateSpaceHeight(height);