# Source: src/ol/canvasfunction.js

    goog.provide('ol.CanvasFunctionType');

    /**
     * A function returning the canvas element (`{HTMLCanvasElement}`)
     * used by the source as an image. The arguments passed to the function are:
     * {@link ol.Extent} the image extent, `{number}` the image resolution,
     * `{number}` the device pixel ratio, {@link ol.Size} the image size, and
     * {@link ol.proj.Projection} the image projection. The canvas returned by
     * this function is cached by the source. The this keyword inside the function
     * references the {@link ol.source.ImageCanvas}.
     *
     * @typedef {function(this:ol.source.ImageCanvas, ol.Extent, number,
     *     number, ol.Size, ol.proj.Projection): HTMLCanvasElement}
     * @todo api
     */
    ol.CanvasFunctionType;