HTML
Living Standard — Last Updated 17 December 2024
Living Standard — Last Updated 17 December 2024
Support in all current engines.
[Exposed =(Window ,Worker ), Serializable , Transferable ]
interface ImageBitmap {
readonly attribute unsigned long width ;
readonly attribute unsigned long height ;
undefined close ();
};
typedef (CanvasImageSource or
Blob or
ImageData ) ImageBitmapSource ;
enum ImageOrientation { " from-image " , " flipY " };
enum PremultiplyAlpha { " none " , " premultiply " , " default " };
enum ColorSpaceConversion { " none " , " default " };
enum ResizeQuality { " pixelated " , " low " , " medium " , " high " };
dictionary ImageBitmapOptions {
ImageOrientation imageOrientation = "from-image";
PremultiplyAlpha premultiplyAlpha = "default";
ColorSpaceConversion colorSpaceConversion = "default";
[EnforceRange ] unsigned long resizeWidth ;
[EnforceRange ] unsigned long resizeHeight ;
ResizeQuality resizeQuality = "low";
};ImageBitmapオブジェクトは過度の待ち時間なしのキャンバスに塗装できるビットマップ画像を表す。
この過度の待ち時間は何かの正確な判断は実装者に委ねるが、一般にビットマップを活用することは、ネットワークI/O、あるいはローカルディスクI/Oを必要とする場合、その後待ち時間はおそらく過度である。一方それが唯一のGPUやシステムRAMからのブロッキングの読み出しを必要とする場合、待ち時間はおそらく許容できる。
promise = self.createImageBitmap(image [, options ])Support in all current engines.
promise = self.createImageBitmap(image, sx, sy, sw, sh [, options ])画像、これはimg要素、SVG image要素、video要素、canvas要素、Blobオブジェクト、ImageDataオブジェクト、または別のImageBitmapオブジェクトである、を取得し、新しいImageBitmapが作成されたときに解決されるpromiseを返す。
ImageBitmapオブジェクトを構築することが全くできない場合、たとえば、与えられたimage データが実際の画像ではないので、代わりにpromiseが却下される。
sx、sy、sw、およびsh引数が指定される場合、ソース画像は与えられたピクセルに切り取られ、元のピクセルに欠けているピクセルは透明な黒に置き換えられる。これらの座標は、CSSピクセルではなく、ソース画像のピクセル座標空間にある。
optionsが指定される場合、ImageBitmapオブジェクトのビットマップデータはoptionsに従って変更される。For example, if the premultiplyAlpha option is set to "premultiply", the bitmap data's color channels are premultiplied by its alpha channel.
ソース画像が有効な状態にない場合、"InvalidStateError" DOMExceptionを拒否する（たとえば、正常に読み込まれなかったimg要素、[[Detached]]内部スロット値がtrueのImageBitmapオブジェクト、data属性値の[[ViewedArrayBuffer]]内部スロットが切り離されているImageDataオブジェクト、データがビットマップイメージとして解釈できないBlobなど）。
スクリプトがソース画像の画像データへのアクセスを許可されていない場合、"SecurityError" DOMExceptionでpromiseを拒否する（たとえば、生成元をまたぐCORSであるvideo、別の生成元からのワーカーのスクリプトで描画されたcanvasなど）。
imageBitmap.close()Support in all current engines.
imageBitmapの基礎となるビットマップデータを解放する。
imageBitmap.widthSupport in all current engines.
imageBitmap.heightSupport in all current engines.
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:
If value's origin-clean flag is not set, then throw a "DataCloneError" DOMException.
Set serialized.[[BitmapData]] to a copy of value's bitmap data.
Their deserialization steps, given serialized, value, and targetRealm, are:
Set value's bitmap data to serialized.[[BitmapData]].
Their transfer steps, given value and dataHolder, are:
If value's origin-clean flag is not set, then throw a "DataCloneError" DOMException.
Set dataHolder.[[BitmapData]] to value's bitmap data.
Unset value's bitmap data.
Their transfer-receiving steps, given dataHolder and value, are:
Set value's bitmap data to dataHolder.[[BitmapData]].
The createImageBitmap(image, options) and createImageBitmap(image sx, sy, sw, sh, options) methods, when invoked, must run these steps:
If either sw or sh is given and is 0, then return a promise rejected with a RangeError.
If either options's resizeWidth or options's resizeHeight is present and is 0, then return a promise rejected with an "InvalidStateError" DOMException.
Check the usability of the image argument. If this throws an exception or returns bad, then return a promise rejected with an "InvalidStateError" DOMException.
Let p be a new promise.
Let imageBitmap be a new ImageBitmap object.
Switch on image:
imgimageIf image's media data has no natural dimensions (e.g., it's a vector graphic with no specified content size) and either options's resizeWidth or options's resizeHeight is not present, then return a promise rejected with an "InvalidStateError" DOMException.
If image's media data has no natural dimensions (e.g., it's a vector graphic with no specified content size), it should be rendered to a bitmap of the size specified by the resizeWidth and the resizeHeight options.
Set imageBitmap's bitmap data to a copy of image's media data, cropped to the source rectangle with formatting. If this is an animated image, imageBitmap'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.
If image is not origin-clean, then set the origin-clean flag of imageBitmap's bitmap to false.
Run this step in parallel:
Resolve p with imageBitmap.
videoIf image's networkState attribute is NETWORK_EMPTY, then return a promise rejected with an "InvalidStateError" DOMException.
Set imageBitmap's bitmap data to a copy of the frame at the current playback position, at the media resource's natural width and natural height (i.e., after any aspect-ratio correction has been applied), cropped to the source rectangle with formatting.
If image is not origin-clean, then set the origin-clean flag of imageBitmap's bitmap to false.
Run this step in parallel:
Resolve p with imageBitmap.
canvasSet imageBitmap's bitmap data to a copy of image's bitmap data, cropped to the source rectangle with formatting.
Set the origin-clean flag of the imageBitmap's bitmap to the same value as the origin-clean flag of image's bitmap.
Run this step in parallel:
Resolve p with imageBitmap.
BlobRun these steps in parallel:
Let imageData be the result of reading image's data. If an error occurs during reading of the object, then reject p with an "InvalidStateError" DOMException and abort these steps.
Apply the image sniffing rules to determine the file format of imageData, with MIME type of image (as given by image's type attribute) giving the official type.
If imageData is not in a supported image file format (e.g., it's not an image at all), or if imageData is corrupted in some fatal way such that the image dimensions cannot be obtained (e.g., a vector graphic with no natural size), then reject p with an "InvalidStateError" DOMException and abort these steps.
Set imageBitmap's bitmap data to imageData, cropped to the source rectangle with formatting. If this is an animated image, imageBitmap'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.
Resolve p with imageBitmap.
ImageDataLet buffer be image's data attribute value's [[ViewedArrayBuffer]] internal slot.
If IsDetachedBuffer(buffer) is true, then return a promise rejected with an "InvalidStateError" DOMException.
Set imageBitmap's bitmap data to image's image data, cropped to the source rectangle with formatting.
Run this step in parallel:
Resolve p with imageBitmap.
ImageBitmapSet imageBitmap's bitmap data to a copy of image's bitmap data, cropped to the source rectangle with formatting.
Set the origin-clean flag of imageBitmap's bitmap to the same value as the origin-clean flag of image's bitmap.
Run this step in parallel:
Resolve p with imageBitmap.
VideoFrameSet imageBitmap's bitmap data to a copy of image's visible pixel data, cropped to the source rectangle with formatting.
Run this step in parallel:
Resolve p with imageBitmap.
Return p.
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:
Let input be the bitmap data being transformed.
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.
Let outputWidth be determined as follows:
resizeWidth member of options is specifiedresizeWidth member of optionsresizeWidth member of options is not specified, but the resizeHeight member is specifiedresizeHeight member of options, divided by the height of sourceRectangle, rounded up to the nearest integerresizeWidth nor resizeHeight are specifiedLet outputHeight be determined as follows:
resizeHeight member of options is specifiedresizeHeight member of optionsresizeHeight member of options is not specified, but the resizeWidth member is specifiedresizeWidth member of options, divided by the width of sourceRectangle, rounded up to the nearest integerresizeWidth nor resizeHeight are specifiedPlace 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.
Let output be the rectangle on the plane denoted by sourceRectangle.
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.
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 "from-image", no extra step is needed.
There used to be a "none" enum value. It was renamed to "from-image". In the future, "none" will be added back with a different meaning.
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:
If val is "default", the color space conversion behavior is implementation-specific, and should be chosen according to the default color space that the implementation uses for drawing images onto the canvas.
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.
Let val be the value of premultiplyAlpha member of options, and then run these substeps:
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.
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.
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.
Return output.
The close() method steps are:
Set this's [[Detached]] internal slot value to true.
Unset this's bitmap data.
The width getter steps are:
If this's [[Detached]] internal slot's value is true, then return 0.
Return this's width, in CSS pixels.
The height getter steps are:
If this's [[Detached]] internal slot's value is true, then return 0.
Return this'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 for scaling the image to preserve the pixelation of the original as much as possible, with minor smoothing as necessary to avoid distorting the image when the target size is not a clean multiple of the original.
To implement "pixelated", for each axis independently, first determine the integer multiple of its natural size that puts it closest to the target size and is greater than zero. Scale it to this integer-multiple-size using nearest neighbor, then scale it the rest of the way to the target size using 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, except for "pixelated" as described above.
このAPIを使用すると、スプライトシートは、プレカットと調製することができる：
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. person = image }),
createImageBitmap( image, 40 , 0 , 40 , 40 ). then( function ( image) { sprites. grass = 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); 一部のオブジェクトにはAnimationFrameProviderインターフェイスミックスインが含まれる。
callback FrameRequestCallback = undefined (DOMHighResTimeStamp time );
interface mixin AnimationFrameProvider {
unsigned long requestAnimationFrame (FrameRequestCallback callback );
undefined cancelAnimationFrame (unsigned long handle );
};
Window includes AnimationFrameProvider ;
DedicatedWorkerGlobalScope includes AnimationFrameProvider ;各AnimationFrameProviderオブジェクトはまた、プロバイダーの内部状態を格納するターゲットオブジェクトを持つ。これは次のように定義される：
AnimationFrameProviderがWindowである場合Windowの関連付けられたDocumentAnimationFrameProviderが DedicatedWorkerGlobalScopeである場合DedicatedWorkerGlobalScope各ターゲットオブジェクトは、アニメーションフレームコールバックのマップ、これは初期は空でなければならない順序付きマップである、およびアニメーションフレームコールバック識別子、これは初期は0でなければならない数、を持つ。
An AnimationFrameProvider provider is considered supported if any of the following are true:
providerがWindowである。
providerの所有者集合におけるすべてのDedicatedWorkerGlobalScopeオブジェクトがサポートされる。
Support in all current engines.
The requestAnimationFrame(callback) method steps are:
If this is not supported, then throw a "NotSupportedError" DOMException.
Let target be this's target object.
Increment target's animation frame callback identifier by one, and let handle be the result.
Let callbacks be target's map of animation frame callbacks.
Set callbacks[handle] to callback.
Return handle.
Support in all current engines.
The cancelAnimationFrame(handle) method steps are:
If this is not supported, then throw a "NotSupportedError" DOMException.
Let callbacks be this's target object's map of animation frame callbacks.
Remove callbacks[handle].
To run the animation frame callbacks for a target object target with a timestamp now:
Let callbacks be target's map of animation frame callbacks.
Let callbackHandles be the result of getting the keys of callbacks.
For each handle in callbackHandles, if handle exists in callbacks:
ワーカー内部では、canvas要素から転送されたOffscreenCanvasと一緒にrequestAnimationFrame()を使用することができる。まず、文書内で、ワーカーに制御を転送する：
const offscreenCanvas = document. getElementById( "c" ). transferControlToOffscreen();
worker. postMessage( offscreenCanvas, [ offscreenCanvas]); 次に、ワーカーにおいて、以下のコードで左から右に移動する矩形を描画する：
let ctx, pos = 0 ;
function draw( dt) {
ctx. clearRect( 0 , 0 , 100 , 100 );
ctx. fillRect( pos, 0 , 10 , 10 );
pos += 10 * dt;
requestAnimationFrame( draw);
}
self. onmessage = function ( ev) {
const transferredCanvas = ev. data;
ctx = transferredCanvas. getContext( "2d" );
draw();
};