Hello, I'm Berg Front-end Factory, I'm learning Xi canvas recently, share some knowledge notes of canvas, Berg is also a novice to canvas, and it is also growing, welcome to the old iron, a classmate Xi, welcome to follow.The Canvas is an element in HTML5 that provides a programmable drawing area that can be controlled and manipulated via J**Ascript. In Canvas, we can use a variety of objects for drawing and interactivity.
These objects can be seen as tools for canvas, and they provide different functions and methods for drawing graphics, adding text, creating gradients, setting shadows, etc. By using these objects, we can draw various shapes, images, text, etc. on the canvas and achieve interactive effects.
The relationship between a canvas and an object can be understood as follows: a canvas provides a drawing area, and an object is a tool used to manipulate and control this drawing area. We can create and use these objects with J.Ascript, and then apply them to the canvas for a variety of drawing and interaction effects.
In Canvas, we can use multiple objects to combine for complex drawing and interactive effects. These objects can be used in conjunction with each other to achieve a variety of functions and effects by calling the object's methods and properties. By controlling and manipulating these objects, we can implement custom drawing and interaction behaviors, making Canvas a powerful and flexible drawing tool.
Context:A context object is a property of a canvas element, which is an object that provides a set of methods and properties for 2D or 3D drawing on a canvas. By getting the context object of the canvas element, we can use the context object's methods to draw different shapes, lines, text, etc.
Image object: Image objects are used to load and process images. We can use the image object to load an external image file and then draw the image on the canvas.
Path object: Path objects are used to draw complex shapes and paths. With the path object, we can define the path using a series of path commands (such as moveto, lineto, arcto, etc.) and then draw the path on the canvas.
Gradient object: Gradient objects are used to create gradient effects. With a gradient object, we can create a linear gradient or a radial gradient, and then apply the gradient to the fills or strokes of the shape.
Shadow object: Shadow objects are used to create a shadow effect for shapes. With shadow objects, we can set properties such as the color, blur, offset, etc., of the shadow, and then apply the shadow to the fill or stroke of the shape.
Text object (text).: A text object is used to draw text on a canvas. With the text object, we can set the style, font, alignment, and other properties of the text, and then draw the text on the canvas.
Image data object (imagedata).: Image data objects are used to process and manipulate pixel data. With the image data object, we can obtain the pixel data of the specified area on the canvas, and then perform pixel-level manipulation and processing.
Audio object (audio).: The audio object is used for audio in the canvas. With the audio object, we can load the audio file and then ** the audio in the canvas to implement functions such as sound effects or backgrounds.
Object (video).:* object is used to load the file in the canvas and then implement features such as processing and processing in the canvas.
Pixel manipulation: Pixel operands are used to directly manipulate and modify pixel data on canvases. Through pixel operants, we can read and modify the color value, transparency and other information of the pixel to achieve pixel-level image processing and special effects.
Animation object: Animated objects are used to create and manage animated effects. By animating objects, we can set properties such as the frame rate, speed, and looping method of the animation, and then achieve a smooth animation effect on the canvas.
Clipping:Crop objects are used to limit the area of the drawing. By cropping an object, we can define an area, and then only the drawing operations within that area will take effect, achieving restrictions and control over the drawing on the canvas.
Touch:Touch objects are used to handle touch events. By touching objects, we can listen to and process the user's touch operations on the canvas to achieve touch interaction effects.
Keyboard object: The keyboard object is used to handle keyboard events. Through the keyboard object, we can listen to and process the user's key actions on the keyboard to achieve keyboard interaction.
In Canvas, we can use j**ascript to manipulate and control objects.
Create Object:First, we need to use j**ascript to create the object. You can create an object using its constructor or literals. For example, you can use new object() or {} to create an empty object.
Set object propertiesOnce the object is created, we can use the point operator or the square bracket operator to set the object's properties. By setting properties, we can define various properties and values of an object that are used to control the behavior and appearance of the object. For example, you can use objectproperty = value to set the properties of the object.
Call the object method:Objects often provide methods to perform a specific action. By calling the methods of the object, we can realize the operation and control of the object. For example, you can use objectmethod() to call the object's methods.
Draw objectsObjects in :canvas are usually used to draw graphics, text, images, etc. By using Canvas's drawing API, we can draw objects onto Canvas. For example, you can use contextfillrect() to draw a rectangular object.
Listen to object events: Some objects may trigger events, such as mouse clicks, keyboard keys, and so on. We can use events to listen for events triggered by objects and perform actions accordingly. For example, you can use objectaddEventListener() to listen for the object's events.
With the above steps, we can manipulate and control the objects in the canvas. Depending on your specific needs, you can choose the appropriate objects and methods to achieve the desired drawing and interaction effects.
Postscript: Berg's front-end workshop has also begun to study canvas, welcome like-minded friends to learn Xi together, and if there are any deficiencies in sharing, please correct them.