This is correct as long as no wild CSS rules are involved. Use the coordinates to select the data on the canvas. To retrieve the color from a pixel of a specific canvas, we are going to : Retrieve the location of the mouse event. The very simplest approach was already posted here. This task is relatively easy to achieve using pure javascript without any kind of library. (from MDN) The amount of scrolling that has been done of the viewport area (orĪny other scrollable element) is taken into account when computing the This includes scrolling, so stuff like scrollTop is not needed: The HTMLElement.getBoundingClientRect method is designed to to handle actual screen position of any element. I'm not sure what's the point of all these answers that loop through parent elements and do all kinds of weird stuff. function relMouseCoords(event)%)` Ĭanvas deliberately has differnt CSS size vs drawingbuffer size This code works perfectly for me, tested in Firefox and Safari but should work for all. To account for this you need to loop through the chain of offsetParents, beginning with the canvas element itself. For a more detailed list of mouse events you could have a read of this. In this case we will use ‘mousemove’ to log the current X and Y coordinates of the mouse to the console. First we set up an event listener for our event: document.addEventListener ('mousemove. To get the current mouse position we are going to trigger a mouse event. It will return the number of pixels it is offset relative to its offsetParent element, which can be something like a div element containing the canvas with a position: relative style applied. To get the current mouse position we are going to trigger a mouse event. If you want to be able to check your coordinates often. ![]() Of course, it was a bit more complicated, but this is the code i want to share with you. Issue a set of commands to display the mouse coordinates in your Microsoft Windows computer. Since the canvas isn't always styled relative to the entire page, the canvas.offsetLeft/Top doesn't always return what you need. I had to display several photos where the user can click over an interesting point and have its coordinates passed through a form. Update (5/5/16): patriques' answer should be used instead, as it's both simpler and more reliable.
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