Clean tainted canvas

Question

Is it possible to clean a tainted canvas?

I have an Openlayers map where user can add layer with CORS restriction. I can't bypass the cors by my proxy config and crossOrigin='anonymus' is not an option.

What I need, it's to be able to remove the " bad " layer and let the user produces the map image.

So I try to:

• Remove the layer who can't be printed
• Try to sync the map
• Try to print

But I always get the cors error. How can I make my map great again without refreshing the browser?

Answer 1

No there is no way to clean a tainted canvas.
Once tainted, it will remain tainted for its whole life.

Not only this, but also drawing this canvas on a second canvas will taint that second canvas too. Even if that canvas has been completely cleared.

So, the only way for you, is to start again from a new canvas element, and to filter out the bad layers before they are drawn.

Answer 2

There is a property crossOrigin in the source of added layer so you can give it the value crossOrigin: "Anonymous" as the following sample

var basemap = new ol.layer.Tile({
        source: new ol.source.TileArcGISRest({
            ratio: 1,
            params: {},
            crossOrigin: "Anonymous",
            url: "http://services.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer"
        })
   })

I hope this will fit