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API

APNG.ifNeeded([ignoreNativeAPNG boolean])

Checks whether there is a need to use the library.

Fulfilled (no value): The browser supports everything for the technology to work, but it does not support APNG. Usually the library should only be used in this case.

If optional argument ignoreNativeAPNG is true, then native APNG support isn't tested.

Rejected (no value): The browser has native support for APNG (if ignoreNativeAPNG not used) or does not support all the necessary technologies for it to work.

APNG.animateImage(img HTMLImageElement)

Creates a canvas element where the APNG animation plays. The img element is removed from the DOM and replaced by canvas. The img element attributes are preserved during replacement.

Fulfilled (no value): The img element is an APNG image.

Rejected (no value): The img element is not an APNG image, or there was an error when processing it. In this case the element is not replaced with canvas.

APNG.releaseCanvas(canvas HTMLCanvasElement)

Detaches canvas from animation loop. May be useful for dynamic created APNG-images. This is a synchronous method, it does not return a result.

APNG.checkNativeFeatures()

Checks which technologies are supported by the browser.

Fulfilled (Features): Returns the Features object with the following fields:

{
    TypedArrays:    boolean
    BlobURLs:       boolean
    requestAnimationFrame: boolean
    pageProtocol:   boolean
    canvas:         boolean
    APNG:           boolean
}

Each field has the value true or false. True means the browser has built-in support for the relevant technology. The pageProtocol field has the value true if the page is loaded over the http or https protocol (the library does not work on pages downloaded over other protocols).

The library can work if all fields except APNG have the value true.

Rejected: N/A.

APNG.parseBuffer(data ArrayBuffer)

Parses binary data from the APNG-file.

Fulfilled (Animation): If the transmitted data are valid APNG, then the Animation object is returned with the following fields:

{
    // Properties
    
    width:      int // image width
    height:     int // image height
    numPlays:   int // number of times to loop this animation.  0 indicates infinite looping.
    playTime:   int // time of full animation cycle in millisecond
    frames: [       // animation frames
        {
            width:  int // frame image width
            height: int // frame image height
            left:   int // frame image horizontal offset 
            top:    int // frame image vertical offset
            delay:  int // frame delay in millisecond
            disposeOp:  int // frame area disposal mode (see spec.)
            blendOp:    int // frame area blend mode (see spec.)
            img:    HTMLImageElement // frame image                   
        }
    ]
    
    // Methods
    
    isPlayed(): boolean     // is animation playing now?  
    isFinished(): boolean   // is animation finished (if numPlays <> 0)? 
    play()                  // play animation (if not playing and not finished)
    rewind()                // rewind animation to initial state and stop it
    addContext(CanvasRenderingContext2D)    // play animation on this canvas context 
                                            // (one animation may be played on many contexts)
    removeContext(CanvasRenderingContext2D) // remove context from animation
}

Rejected (string): The file is not valid APNG, or there was a parsing error. Returns a string with an error message.

APNG.parseURL(url string)

Downloads an image from the supplied URL and parses it.

Fulfilled (Animation): If the downloaded data are valid APNG, then the Animation object is returned (see APNG.parseBuffer). The same Animation object is returned for the same URL.

Rejected (mixed): There was an error when downloading or parsing.

APNG.animateContext(url string, CanvasRenderingContext2D context)

Downloads an image from the supplied URL, parses it, and plays it in the given canvas environment.

Fulfilled (Animation): Similar to output of APNG.parseURL.

Rejected (mixed): There was an error when downloading or parsing.