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Get Line co-ordinates in Javascript

开发者 https://www.devze.com 2023-03-19 17:44 出处:网络
I am drawing lines using Canvas (HTML 5), since lines/shapes are not stored as objects in Canvas, I cannot attach unique events to it (eg onmouseclick)

I am drawing lines using Canvas (HTML 5), since lines/shapes are not stored as objects in Canvas, I cannot attach unique events to it (eg onmouseclick)

I wish to attach a onmouseover event to a line, is it possible by getting to know if the mouse if over a particular line (using its 2 X and 2 Y co-ordinates) in Canvas using Javascript. Would this work for different line widths (eg: 2,5 pixels)

Want to avoid using SVG as the entire 开发者_高级运维project is built on Canvas

Please advise.


You would need to use math formulas to calculate the area of the line and whether a certain point intersects with it.

Here's a basic example:

  • Find mouse coordinates relative to position of the canvas (How to find mouse pos on element)
  • Calculate whether mouse x/y is inside some rectangle (Point in rectangle formula)
  • Done.


There is a function isPointInPath(x,y). It will return true if a point is on the current path. You will have to call that for every line you want to check and the best way to do that is at the same time as you draw.


The best way is using some canvas frameworks. Look at "LibCanvas :: Creating Lines" (dont forget to dblClick at canvas)

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