What APIs does canvas have?

Canvas apis include getContext(), fillRect(), strokeRect(), clearRect(), beginPath(), closePath(), moveTo(), lineTo(), arc(), arcTo(), fill(), stroke(), translate(), rotate(), scale(), drawImage(), etc.

# Operating system for this tutorial: Windows 10 system, Dell G3 computer.

Canvas is a tag in HTML5 that can be used to draw graphics, animations and other visual effects on web pages. As a programmer, it is very important to understand the Canvas API. Below I will introduce several commonly used Canvas APIs.

getContext(): This is one of the most important APIs of Canvas, which is used to obtain the drawing context. Through the getContext() method, we can specify the type of drawing context, such as 2D drawing context or WebGL drawing context. For example, the 2D drawing context can be obtained through the following code:

const canvas = document.getElementById('myCanvas');
const ctx = canvas.getContext('2d');

fillRect() and strokeRect(): These two APIs are used to draw rectangles. fillRect(x, y, width, height) is used to fill the rectangle at the specified position and size, while strokeRect(x, y, width, height) is used to draw the border of the rectangle at the specified position and size.

clearRect(): This API is used to clear the rectangular area of ​​​​the specified position and size. You can use it to perform the eraser function.

beginPath() and closePath(): These two APIs are used to define paths. beginPath() is used to start drawing a new path, and closePath() is used to close the path.

moveTo() and lineTo(): ​​These two APIs are used to move the brush on the path. moveTo(x, y) is used to move the pen to the specified coordinate point, while lineTo(x, y) is used to draw a straight line from the current position to the specified coordinate point.

arc() and arcTo(): ​​These two APIs are used to draw arcs. arc(x, y, radius, startAngle, endAngle, anticlockwise) is used to draw an arc or partial circle, while arcTo(x1, y1, x2, y2, radius) is used to draw an arc connecting two tangents.

fill() and stroke(): These two APIs are used to fill and stroke paths. fill() is used to fill the interior of the path, while stroke() is used to stroke the boundary of the path.

save() and restore(): These two APIs are used to save and restore the drawing state. save() is used to save the current drawing state, including transformation matrix, clipping area, etc., while restore() is used to restore the previously saved drawing state.

translate(), rotate() and scale(): These three APIs are used to transform drawings. translate(x, y) is used to translate the origin of the drawing, rotate(angle) is used to rotate the drawing, and scale(x, y) is used to scale the drawing.

drawImage(): This API is used to draw images. You can draw a specified image through drawImage(image, x, y), or you can draw an image of a specified size through drawImage(image, x, y, width, height).

This is only a small part of the Canvas API. There are many other APIs that can be used to draw graphics, handle events, etc. As programmers, we need to deeply study and understand the API of Canvas so that we can better utilize it to achieve various visual effects.

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