I´m not able to get the right color at the current mouse cursor position after having resized the canvas
. The reason for resizing the canvas
is adapting it to different screen sizes. Unfortunately the color data does not get updated after having resized. How can I fix this?
My code is on JS Fiddle (the JS part is also below).
You can see a demonstration of the issue in this video .
var actualColor = "ffffff";
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
context.canvas.width = 150;
context.canvas.height = 200;
context.beginPath(); context.rect(0,0,150,100); context.fillStyle="red"; context.fill(); context.closePath();
context.beginPath(); context.rect(0,100,150,100); context.fillStyle="blue"; context.fill(); context.closePath();
window.addEventListener('load', function(){
resize();
});
window.addEventListener('resize', function(){
resize();
});
/**
* Scale proportionally: If the width of the canvas > the height, the canvas height
* equals the height of the browser window. Else, the canvas width equals the width of the browser window.
* If the window is resized, the size of the canvas changes dynamically.
*/
function resize() {
var ratio = canvas.width / canvas.height;
var canvas_height = window.innerHeight;
canvas_height -= 130; // remove later
var canvas_width = canvas_height * ratio;
if (canvas_width > window.innerWidth) {
canvas_width = window.innerWidth;
canvas_height = canvas_width / ratio;
}
canvas.style.width = canvas_width + 'px';
canvas.style.height = canvas_height + 'px';
}
// get the color at the mouse position
$('#canvas').mousemove(function (e) {
var pos = {
x:canvas.offsetLeft,
y:canvas.offsetTop
}
var x = e.pageX - pos.x;
var y = e.pageY - pos.y;
var c = canvas.getContext('2d');
var p = c.getImageData(x, y, 1, 1).data;
actualColor = ("000000" + rgbToHex(p[0], p[1], p[2])).slice(-6);
$('#colorOutput').css("background-color", "#" + actualColor);
$('#status').html(actualColor);
});
function rgbToHex(r, g, b) {
return componentToHex(r) + componentToHex(g) + componentToHex(b);
}
function componentToHex(c) {
var hex = c.toString(16);
return hex.length == 1 ? "0" + hex : hex;
}
The Problem is you are zooming the canvas. You will have to set its real width and height, and then redraw it.
Check this out: http://jsfiddle.net/vyjwLfuc/
function resize() {
...
canvas.width = canvas_width
canvas.height = canvas_height
draw()
}
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.