1. 8.8 Images
    2. 8.9 Animation Frames

8.8 Images

[Exposed=(Window,Worker), Serializable, Transferable]
interface ImageBitmap {
  readonly attribute unsigned long width;
  readonly attribute unsigned long height;
  void close();
};

typedef (CanvasImageSource or
         Blob or
         ImageData) ImageBitmapSource;

enum ImageOrientation { "none", "flipY" };
enum PremultiplyAlpha { "none", "premultiply", "default" };
enum ColorSpaceConversion { "none", "default" };
enum ResizeQuality { "pixelated", "low", "medium", "high" };

dictionary ImageBitmapOptions {
  ImageOrientation imageOrientation = "none";
  PremultiplyAlpha premultiplyAlpha = "default";
  ColorSpaceConversion colorSpaceConversion = "default";
  [EnforceRange] unsigned long resizeWidth;
  [EnforceRange] unsigned long resizeHeight;
  ResizeQuality resizeQuality = "low";
};

An ImageBitmap object represents a bitmap image that can be painted to a canvas without undue latency.

The exact judgement of what is undue latency of this is left up to the implementer, but in general if making use of the bitmap requires network I/O, or even local disk I/O, then the latency is probably undue; whereas if it only requires a blocking read from a GPU or system RAM, the latency is probably acceptable.

promise = self . createImageBitmap(image [, options ])
promise = self . createImageBitmap(image, sx, sy, sw, sh [, options ])

Takes image, which can be an img element, an SVG image element, a video element, a canvas element, a Blob object, an ImageData object, or another ImageBitmap object, and returns a promise that is resolved when a new ImageBitmap is created.

If no ImageBitmap object can be constructed, for example because the provided image data is not actually an image, then the promise is rejected instead.

If sx, sy, sw, and sh arguments are provided, the source image is cropped to the given pixels, with any pixels missing in the original replaced by transparent black. These coordinates are in the source image's pixel coordinate space, not in CSS pixels.

If options is provided, the ImageBitmap object's bitmap data is modified according to options. For example, if the premultiplyAlpha option is set to "premultiply", the bitmap data's color channels are premultiplied by its alpha channel.

Rejects the promise with an "InvalidStateError" DOMException if the source image is not in a valid state (e.g. an img element that hasn't loaded successfully, an ImageBitmap object whose [[Detached]] internal slot value is true, an ImageData object whose data attribute value's [[Detached]] internal slot value is true, or a Blob whose data cannot be interpreted as a bitmap image).

Rejects the promise with a "SecurityError" DOMException if the script is not allowed to access the image data of the source image (e.g. a video that is CORS-cross-origin, or a canvas being drawn on by a script in a worker from another origin).

imageBitmap . close()

Releases imageBitmap's underlying bitmap data.

imageBitmap . width

Returns the intrinsic width of the image, in CSS pixels.

imageBitmap . height

Returns the intrinsic height of the image, in CSS pixels.

An ImageBitmap object whose [[Detached]] internal slot value is false always has associated bitmap data, with a width and a height. However, it is possible for this data to be corrupted. If an ImageBitmap object's media data can be decoded without errors, it is said to be fully decodable.

An ImageBitmap object's bitmap has an origin-clean flag, which indicates whether the bitmap is tainted by content from a different origin. The flag is initially set to true and may be changed to false by the steps of createImageBitmap().


ImageBitmap objects are serializable objects and transferable objects.

Their serialization steps, given value and serialized, are:

  1. Set serialized.[[BitmapData]] to a copy of value's bitmap data.

  2. Set serialized.[[OriginClean]] to true if value's origin-clean flag is set, and false otherwise.

Their deserialization steps, given serialized and value, are:

  1. Set value's bitmap data to serialized.[[BitmapData]].

  2. If serialized.[[OriginClean]] is true, set value's origin-clean flag.

Their transfer steps, given value and dataHolder, are:

  1. Set dataHolder.[[BitmapData]] to value's bitmap data.

  2. Set dataHolder.[[OriginClean]] to true if value's origin-clean flag is set, and false otherwise.

  3. Unset value's bitmap data.

Their transfer-receiving steps, given dataHolder and value, are:

  1. Set value's bitmap data to dataHolder.[[BitmapData]].

  2. If dataHolder.[[OriginClean]] is true, set value's origin-clean flag.


An ImageBitmap object can be obtained from a variety of different objects, using the createImageBitmap() method. When invoked, the method must act as follows:

If image is an img element
If image is an SVG image element
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. If image is not completely available, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  3. If image's media data has no intrinsic dimensions (e.g. it's a vector graphic with no specified content size), and both or either of the resizeWidth and resizeHeight options are not specified, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  4. If image's media data has no intrinsic dimensions (e.g. it's a vector graphics with no specified content size), it should be rendered to a bitmap of the size specified by the resizeWidth and the resizeHeight options.

  5. If the sw and sh arguments are not specified and image's media data has both or either of its intrinsic width and intrinsic height values equal to 0, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  6. If the sh argument is not specified and image's media data has an intrinsic height of 0, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  7. Create a new ImageBitmap object.

  8. Let the ImageBitmap object's bitmap data be a copy of image's media data, cropped to the source rectangle with formatting. If this is an animated image, the ImageBitmap object's bitmap data must only be taken from the default image of the animation (the one that the format defines is to be used when animation is not supported or is disabled), or, if there is no such image, the first frame of the animation.

  9. If the origin of image's image is not the same origin as the origin specified by the entry settings object, then set the origin-clean flag of the ImageBitmap object's bitmap to false.

  10. Return a new promise, but continue running these steps in parallel.

  11. Resolve the promise with the new ImageBitmap object as the value.

If image is a video element
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. If the video element's networkState attribute is NETWORK_EMPTY, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  3. If the video element's readyState attribute is either HAVE_NOTHING or HAVE_METADATA, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  4. Create a new ImageBitmap object.

  5. Let the ImageBitmap object's bitmap data be a copy of the frame at the current playback position, at the media resource's intrinsic width and intrinsic height (i.e. after any aspect-ratio correction has been applied), cropped to the source rectangle with formatting.

  6. If the origin of the video element is not the same origin as the origin specified by the entry settings object, then set the origin-clean flag of the ImageBitmap object's bitmap to false.

  7. Return a new promise, but continue running these steps in parallel.

  8. Resolve the promise with the new ImageBitmap object as the value.

If image is a canvas element
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. If the canvas element's bitmap has either a horizontal dimension or a vertical dimension equal to zero, then return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  3. Create a new ImageBitmap object.

  4. Let the ImageBitmap object's bitmap data be a copy of the canvas element's bitmap data, cropped to the source rectangle with formatting.

  5. Set the origin-clean flag of the ImageBitmap object's bitmap to the same value as the origin-clean flag of the canvas element's bitmap.

  6. Return a new promise, but continue running these steps in parallel.

  7. Resolve the promise with the new ImageBitmap object as the value.

If image is a Blob object
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. Return a new promise, but continue running these steps in parallel.

  3. Read the Blob object's data. If an error occurs during reading of the object, then reject the promise with an "InvalidStateError" DOMException, and abort these steps.

  4. Apply the image sniffing rules to determine the file format of the image data, with MIME type of the Blob (as given by the Blob object's type attribute) giving the official type.

  5. If the image data is not in a supported image file format (e.g. it's not an image at all), or if the image data is corrupted in some fatal way such that the image dimensions cannot be obtained (e.g. a vector graphic with no intrinsic size), then reject the promise with an "InvalidStateError" DOMException, and abort these steps.

  6. Create a new ImageBitmap object.

  7. Let the ImageBitmap object's bitmap data be the image data read from the Blob object, cropped to the source rectangle with formatting. If this is an animated image, the ImageBitmap object's bitmap data must only be taken from the default image of the animation (the one that the format defines is to be used when animation is not supported or is disabled), or, if there is no such image, the first frame of the animation.

  8. Resolve the promise with the new ImageBitmap object as the value.

If image is an ImageData object
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. If the image object's data attribute value's [[Detached]] internal slot value is true, return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  3. Create a new ImageBitmap object.

  4. Let the ImageBitmap object's bitmap data be the image data given by the ImageData object, cropped to the source rectangle with formatting.

  5. Return a new promise, but continue running these steps in parallel.

  6. Resolve the promise with the new ImageBitmap object as the value.

If image is an ImageBitmap object
  1. If either the sw or sh arguments are specified but zero, return a promise rejected with an "IndexSizeError" DOMException and abort these steps.

  2. If image's [[Detached]] internal slot value is true, return a promise rejected with an "InvalidStateError" DOMException and abort these steps.

  3. Create a new ImageBitmap object.

  4. Let the ImageBitmap object's bitmap data be a copy of the image argument's bitmap data, cropped to the source rectangle with formatting.

  5. Set the origin-clean flag of the ImageBitmap object's bitmap to the same value as the origin-clean flag of the bitmap of the image argument.

  6. Return a new promise, but continue running these steps in parallel.

  7. Resolve the promise with the new ImageBitmap object as the value.

When the steps above require that the user agent crop bitmap data to the source rectangle with formatting, the user agent must run the following steps:

  1. Let input be the bitmap data being transformed.

  2. If either or both of resizeWidth and resizeHeight members of options are less than or equal to 0, then return a promise rejected with "InvalidStateError" DOMException and abort these steps.

  3. If sx, sy, sw and sh are specified, let sourceRectangle be a rectangle whose corners are the four points (sx, sy), (sx+sw, sy),(sx+sw, sy+sh), (sx,sy+sh). Otherwise let sourceRectangle be a rectangle whose corners are the four points (0,0), (width of input, 0), (width of input, height of input), (0, height of input).

    If either sw or sh are negative, then the top-left corner of this rectangle will be to the left or above the (sx, sy) point.

  4. Clip sourceRectangle to the dimensions of input.

  5. Let outputWidth be determined as follows:

    If the resizeWidth member of options is specified
    the value of the resizeWidth member of options
    If the resizeWidth member of options is not specified, but the resizeHeight member is specified
    the width of sourceRectangle, times the value of the resizeHeight member of options, divided by the height of sourceRectangle, rounded up to the nearest integer
    If neither resizeWidth nor resizeHeight are specified
    the width of sourceRectangle
  6. Let outputHeight be determined as follows:

    If the resizeHeight member of options is specified
    the value of the resizeHeight member of options
    If the resizeHeight member of options is not specified, but the resizeWidth member is specified
    the height of sourceRectangle, times the value of the resizeWidth member of options, divided by the width of sourceRectangle, rounded up to the nearest integer
    If neither resizeWidth nor resizeHeight are specified
    the height of sourceRectangle
  7. Place input on an infinite transparent black grid plane, positioned so that its top left corner is at the origin of the plane, with the x-coordinate increasing to the right, and the y-coordinate increasing down, and with each pixel in the input image data occupying a cell on the plane's grid.

  8. Let output be the rectangle on the plane denoted by sourceRectangle.

  9. Scale output to the size specified by outputWidth and outputHeight. The user agent should use the value of the resizeQuality option to guide the choice of scaling algorithm.

  10. If the value of the imageOrientation member of options is "flipY", output must be flipped vertically, disregarding any image orientation metadata of the source (such as EXIF metadata), if any. [EXIF]

    If the value is "none", no extra step is required.

  11. If image is an img element or a Blob object, let val be the value of the colorSpaceConversion member of options, and then run these substeps:

    1. If val is "default", the color space conversion behavior is implementation-specific, and should be chosen according to the color space that the implementation uses for drawing images onto the canvas.

    2. If val is "none", output must be decoded without performing any color space conversions. This means that the image decoding algorithm must ignore color profile metadata embedded in the source data as well as the display device color profile.

    The native color space of canvas is currently unspecified, but this is expected to change in the future.

  12. Let val be the value of premultiplyAlpha member of options, and then run these substeps:

    1. If val is "default", the alpha premultiplication behavior is implementation-specific, and should be chosen according to implementation deems optimal for drawing images onto the canvas.

    2. If val is "premultiply", the output that is not premultiplied by alpha must have its color components multiplied by alpha and that is premultiplied by alpha must be left untouched.

    3. If val is "none", the output that is not premultiplied by alpha must be left untouched and that is premultiplied by alpha must have its color components divided by alpha.

  13. Return output.

When the close() method is called, the user agent must run these steps:

  1. Set this ImageBitmap object's [[Detached]] internal slot value to true.

  2. Unset this ImageBitmap object's bitmap data.

The width attribute's getter must run these steps:

  1. If this ImageBitmap object's [[Detached]] internal slot's value is true, then return 0.

  2. Return this ImageBitmap object's width, in CSS pixels.

The height attribute's getter must run these steps:

  1. If this ImageBitmap object's [[Detached]] internal slot's value is true, then return 0.

  2. Return this ImageBitmap object's height, in CSS pixels.

The ResizeQuality enumeration is used to express a preference for the interpolation quality to use when scaling images.

The "pixelated" value indicates a preference to scale the image that maximizes the appearance. Scaling algorithms that "smooth" colors are acceptable, such as bilinear interpolation.

The "low" value indicates a preference for a low level of image interpolation quality. Low-quality image interpolation may be more computationally efficient than higher settings.

The "medium" value indicates a preference for a medium level of image interpolation quality.

The "high" value indicates a preference for a high level of image interpolation quality. High-quality image interpolation may be more computationally expensive than lower settings.

Bilinear scaling is an example of a relatively fast, lower-quality image-smoothing algorithm. Bicubic or Lanczos scaling are examples of image-scaling algorithms that produce higher-quality output. This specification does not mandate that specific interpolation algorithms be used unless the value is "pixelated".

Using this API, a sprite sheet can be precut and prepared:

var sprites = {};
function loadMySprites() {
  var image = new Image();
  image.src = 'mysprites.png';
  var resolver;
  var promise = new Promise(function (arg) { resolver = arg });
  image.onload = function () {
    resolver(Promise.all([
      createImageBitmap(image,  0,  0, 40, 40).then(function (image) { sprites.woman = image }),
      createImageBitmap(image, 40,  0, 40, 40).then(function (image) { sprites.man   = image }),
      createImageBitmap(image, 80,  0, 40, 40).then(function (image) { sprites.tree  = image }),
      createImageBitmap(image,  0, 40, 40, 40).then(function (image) { sprites.hut   = image }),
      createImageBitmap(image, 40, 40, 40, 40).then(function (image) { sprites.apple = image }),
      createImageBitmap(image, 80, 40, 40, 40).then(function (image) { sprites.snake = image })
    ]));
  };
  return promise;
}

function runDemo() {
  var canvas = document.querySelector('canvas#demo');
  var context = canvas.getContext('2d');
  context.drawImage(sprites.tree, 30, 10);
  context.drawImage(sprites.snake, 70, 10);
}

loadMySprites().then(runDemo);

8.9 Animation Frames

Support: requestanimationframeChrome for Android 59+Chrome 24+iOS Safari 7.0+UC Browser for Android 11.4+Firefox 23+IE 10+Samsung Internet 4+Opera Mini NoneSafari 6.1+Android Browser 4.4+Edge 12+Opera 15+

Source: caniuse.com

Each Document has a list of animation frame callbacks, which must be initially empty, and an animation frame callback identifier, which is a number which must initially be zero.

When the requestAnimationFrame() method is called, the user agent must run the following steps:

  1. Let document be this Window object's associated Document.

  2. Increment document's animation frame callback identifier by one.

  3. Append the method's argument to document's list of animation frame callbacks, associated with document's animation frame callback identifier's current value.

  4. Return document's animation frame callback identifier's current value.

When the cancelAnimationFrame() method is called, the user agent must run the following steps:

  1. Let document be this Window object's associated Document.

  2. Find the entry in document's list of animation frame callbacks that is associated with the value given by the method's argument.

  3. If there is such an entry, remove it from document's list of animation frame callbacks.

When the user agent is to run the animation frame callbacks for a Document doc with a timestamp now, it must run the following steps:

  1. Let callbacks be a list of the entries in doc's list of animation frame callbacks, in the order in which they were added to the list.

  2. Set doc's list of animation frame callbacks to the empty list.

  3. For each entry in callbacks, in order: invoke the callback, passing now as the only argument, and if an exception is thrown, report the exception. [WEBIDL]