first normalize the mouse coordinates from 0 to 1 (0,0) top left // off canvas and (1,1) bottom right by dividing by the bounds width and height mouse.x / bounds.width mouse.y / bounds.height // then scale to canvas. It's used when you're not sure if x has been declared. To get the correct canvas coordinate you need to scale the mouse coordinates to match the canvas resolution coordinates. This is trivial to accomplish if you only need to support specific browsers, but there are differences between f.ex. You don't need to use typeof x != 'undefined' here. To draw on the canvas, a class will be created with three methods: startDrawing, drawSketch, and stopDrawing. Easiest way is probably to add a onmousemove event listener to the canvas element, and then you can get the coordinates relative to the canvas from the event itself. , and then inside the if (draw) you have a context =. You have, on your fourth line, in the global scope a var context =. Var canvas = document.getElementById('canvas') Ĭanvas.addEventListener('click', function (event) Ĭontext.moveTo(prevCoord.x, prevCoord.y)
#Javascript mouse coordinates canvas code
The code I have for this is below, and one concern of mine is how I'm storing the coordinates of the mouse's position each time it moves. Answer: To determine the exact x and y coordinates of a mouse event, use the following properties: event.screenX, event.screenY (the screen x and y coordinates) event.clientX, event.clientY (coordinates relative to the top left corner of the browser window or frame). Only by clicking again will the drawing cease. Once the user clicks the mouse, the user is allowed to drag the mouse wherever they want within the canvas and a line will be drawn from where they started moving the mouse to where the mouse stopped. Window.I have a small JS application that allows a user, after clicking on a canvas, to draw a picture. and then recalculate the canvas offsets
#Javascript mouse coordinates canvas how to
listen for window resizing (and scrolling) events Answers related to mouse coordinates not match with canvas coordinate check if two rectangles overlap javascript canvas How to make move able triangle in. Mouse Coordinates Not Math With Canvas Coordinates In Js With Code Examples In this article, the solution of Mouse Coordinates Not Math With Canvas. a function to recalculate the canvas offsets This code listens for window resizing events and recalculates the offsets used in mouse event handlers: // variables holding the current canvas offset position Thus, responsive design requires that the canvas offset position be recalculated when the window is resized - and also recalculated when the window is scrolled. With being able to pinpoint the mouse position x and y of the mouse on a canvas, what i would like to do is have an image move in the opposite direction. Getting Mouse Position With Javascript Within Canvas Getting mouse location in canvas duplicate How to get the coordinates of a mouse click on a canvas. Canvas apps often rely heavily on user interaction with the mouse, but when the window is resized, the mouse event coordinates that canvas relies on are likely changed because resizing causes the canvas to be offset in a different position relative to the window.
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