How to use a and z in the SVG Path command and what are its parameters explanations?

Detailed explanation of SVG path commands a and z and parameter interpretation

The SVG path definition contains many commands and parameters, which together determine the shape and position of the path. This article will explain the usage of a and z commands in detail through examples and analyze path parameters in depth.

The example path is defined as follows:

 <code>offset: path("m 100,0 a 100 100 0 1 1 -.1 0 z");</code>

a command draws an ellipse arc, and the z command closes the path. Let's analyze one by one:

First, m 100,0 moves the brush to coordinates (100, 0) as the starting point of the path.

Next is the command a :

 <code>a 100 100 0 1 1 -.1 0</code>

The full format of the command a is:

 <code>a rx ry x-axis-rotation large-arc-flag sweep-flag dx dy</code>

• rx and ry are the x-radius and y-radius of the elliptical arc respectively, and here are 100, representing a circle.
• x-axis-rotation is the x-axis rotation angle, where 0 means no rotation.
• large-arc-flag and sweep-flag determine the size and direction of the arc, respectively. All of them are 1 here, indicating that a large arc is drawn and clockwise.
• dx and dy are the relative coordinate offsets of the end point relative to the start point, here are -0.1 and 0.

Why is the end coordinate (-0.1, 0) instead of (0, 0)? Because if the end point is (0, 0), a complete circle cannot be formed and the path will return directly from the starting point to the end point. Use (-0.1, 0) to draw a nearly complete circle, avoiding overlap with the starting point, which may be more advantageous in some path processing.

Finally, the z command closes the path, connecting the end point and the start point.

a and z use lowercase letters to use relative coordinates, while uppercase letters indicate absolute coordinates. In this example, relative coordinates are used to make the path description more concise and easy to understand.

Through the above analysis, we have a clearer understanding of the usage and parameter meaning of the SVG path commands a and z .

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