HTML and CSS Reference
In-Depth Information
The Canvas Pixel Manipulation API
The Canvas Pixel Manipulation API gives us the ability to “get,” “put,” and “change” indi-
vidual pixels, utilizing what is known as the CanvasPixelArray interface. ImageData is the
base object type for this manipulation, and an instance of this object is created with the cre-
ateImageData() function call. Let's start there.
The createImageData() function sets aside a portion of memory to store an individual
pixel's worth of data based on the following three constructors:
imagedata = context. createImageData
createImageData (sw, sh)
imagedata = context.
(sw, sh)
The sw and sh parameters represent the width and height values for the ImageData
object. For example, imagedata=createImageData(100,100) would create a 100×100
area of memory in which to store pixel data.
imagedata = context. createImageData
createImageData (imagedata)
imagedata = context.
The imagedata parameter represents a separate instance of ImageData . This constructor
creates a new ImageData object with the same width and height as the parameter
ImageData .
imagedata = context. createImageData
createImageData (()
This constructor returns a blank ImageData instance.
imagedata = context.
ImageData attributes
An ImageData object contains three attributes:
This returns the height in pixels of the ImageData instance.
This returns the width in pixels of the ImageData instance.
This returns a single-dimensional array of pixels representing the image data. Image data
this data array starts a new pixel. The four elements in the array represent the red, green,
blue, and alpha transparency values of a single pixel.
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