FabricJS objects not relative to canvas resize

问题

I'm using FabricJS to create a fullscreen canvas and save the changes serverside. Before loading it I resize the canvas & background so that on every page-load the canvas fits inside the users window.

canvas.setHeight($(window).height());
canvas.setWidth($(window).width());
canvas.backgroundImage.width = $(window).width();
canvas.backgroundImage.height = $(window).height();

The problem is that the canvas & background get adjusted but not the objects. They keep the same position relative to the screen and don't change size so are incorrent on other screensizes. How can this problem be solved?

回答1:

After a lot of trying I found a solution thanks to a hint from AndreaBogazzi. When changing the background/canvas size/position the objects do not keep there size/position relative to the background/canvas.

That's why it's better to use the zoom functionality, this way all of the canvas elements gets adjusted the same way relative to each other:

// background: background image
// zoom: zoom amount usable with canvas.setZoom(zoom).

if (background.width < $(window).width()) {
    zoom = $(window).height() / background.height;

    if ((zoom * background.width) > $(window).width()) {
        zoom = $(window).width() / background.width;
    }

} else {
    zoom = $(window).width() / background.width;

    if ((zoom * background.height) > $(window).height()) {
        zoom = $(window).height() / background.height;
    }
}
canvas.setZoom(zoom );

This will result in the canvas always being it's maximum size without breaking ratio, without leaving the screen and with all the elements keeping the right position and height.

来源：https://stackoverflow.com/questions/34874844/fabricjs-objects-not-relative-to-canvas-resize

标签

javascript

jquery

html5

canvas

fabricjs