獲取鼠標點擊位置

Question

我正在使用此色輪 ，我想在色輪上添加黑色封面，這樣，當使用色輪下的滑塊更改hsv的值（v）時，色輪將變暗。

我在canvas添加了一個包裝div ，並在wrapper添加了另一個div（ overlay ），並將背景色設置為黑色。 然后，將wrapper的位置設置為relative ，對於overlay ，將位置設置為absolute 。

（我將wrapper設置為relative以便overlay （with為absolute ）將包含在wrapper 。）

由於wrapper設置為relative ，因此色輪選擇不准確。 選擇器沒有完全跟隨鼠標。

我認為可以通過編輯以下代碼來解決該問題：（在redraw()函數的第69行。）

currentX = e.pageX - c.offsetLeft - radiusPlusOffset || currentX;
currentY = e.pageY - c.offsetTop - radiusPlusOffset  || currentY;

但是我不知道該怎么改變。 即使wrapper設置為relative如何使選擇器指針跟隨鼠標？

的jsfiddle

 (function() { // Declare constants and variables to help with minification // Some of these are inlined (with comments to the side with the actual equation) var doc = document; doc.c = doc.createElement; ba = b.appendChild; var width = c.width = c.height = 400, label = ba(doc.c("p")), input = ba(doc.c("input")), imageData = a.createImageData(width, width), pixels = imageData.data, oneHundred = input.value = input.max = 100, circleOffset = 10, diameter = 380, //width-circleOffset*2, radius = 190, //diameter / 2, radiusPlusOffset = 200, //radius + circleOffset radiusSquared = radius * radius, two55 = 255, currentY = oneHundred, currentX = -currentY, wheelPixel = 16040; // circleOffset*4*width+circleOffset*4; // Math helpers var math = Math, PI = math.PI, PI2 = PI * 2, sqrt = math.sqrt, atan2 = math.atan2; // Setup DOM properties b.style.textAlign = "center"; label.style.font = "2em courier"; input.type = "range"; // Load color wheel data into memory. for (y = input.min = 0; y < width; y++) { for (x = 0; x < width; x++) { var rx = x - radius, ry = y - radius, d = rx * rx + ry * ry, rgb = hsvToRgb( (atan2(ry, rx) + PI) / PI2, // Hue sqrt(d) / radius, // Saturation 1 // Value ); // Print current color, but hide if outside the area of the circle pixels[wheelPixel++] = rgb[0]; pixels[wheelPixel++] = rgb[1]; pixels[wheelPixel++] = rgb[2]; pixels[wheelPixel++] = d > radiusSquared ? 0 : two55; } } // Bind Event Handlers input.onchange = redraw; c.onmousedown = doc.onmouseup = function(e) { // Unbind mousemove if this is a mouseup event, or bind mousemove if this a mousedown event doc.onmousemove = /p/.test(e.type) ? 0 : (redraw(e), redraw); } // Handle manual calls + mousemove event handler + input change event handler all in one place. function redraw(e) { // Only process an actual change if it is triggered by the mousemove or mousedown event. // Otherwise e.pageX will be undefined, which will cause the result to be NaN, so it will fallback to the current value currentX = e.pageX - c.offsetLeft - radiusPlusOffset || currentX; currentY = e.pageY - c.offsetTop - radiusPlusOffset || currentY; // Scope these locally so the compiler will minify the names. Will manually remove the 'var' keyword in the minified version. var theta = atan2(currentY, currentX), d = currentX * currentX + currentY * currentY; // If the x/y is not in the circle, find angle between center and mouse point: // Draw a line at that angle from center with the distance of radius // Use that point on the circumference as the draggable location if (d > radiusSquared) { currentX = radius * math.cos(theta); currentY = radius * math.sin(theta); theta = atan2(currentY, currentX); d = currentX * currentX + currentY * currentY; } label.textContent = b.style.background = hsvToRgb( (theta + PI) / PI2, // Current hue (how many degrees along the circle) sqrt(d) / radius, // Current saturation (how close to the middle) input.value / oneHundred // Current value (input type="range" slider value) )[3]; // Reset to color wheel and draw a spot on the current location. a.putImageData(imageData, 0, 0); // Heart: a.font = "1em arial"; a.fillText("♥", currentX + radiusPlusOffset - 4, currentY + radiusPlusOffset + 4); } // Created a shorter version of the HSV to RGB conversion function in TinyColor // https://github.com/bgrins/TinyColor/blob/master/tinycolor.js function hsvToRgb(h, s, v) { h *= 6; var i = ~~h, f = h - i, p = v * (1 - s), q = v * (1 - f * s), t = v * (1 - (1 - f) * s), mod = i % 6, r = [v, q, p, p, t, v][mod] * two55, g = [t, v, v, q, p, p][mod] * two55, b = [p, p, t, v, v, q][mod] * two55; return [r, g, b, "rgb(" + ~~r + "," + ~~g + "," + ~~b + ")"]; } // Kick everything off redraw(0); /* // Just an idea I had to kick everything off with some changing colors… // Probably no way to squeeze this into 1k, but it could probably be a lot smaller than this: currentX = currentY = 1; var interval = setInterval(function() { currentX--; currentY*=1.05; redraw(0) }, 7); setTimeout(function() { clearInterval(interval) }, 700) */ })(); 

 #wrapper { width: 400px; height: 400px; position: relative; } #blackBackground { background-color: black; width: 100%; height: 100%; position: absolute; border-radius: 50%; opacity: .5; pointer-events: none; } 

 <div> Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Aenean commodo ligula eget dolor. Aenean massa. Cum sociis natoque penatibus et magnis dis parturient montes, nascetur ridiculus mus. Donec quam felis, ultricies nec, pellentesque eu, pretium quis, sem. Nulla consequat massa quis enim. Donec pede justo, fringilla vel, aliquet nec, vulputate eget, arcu. In enim justo, rhoncus ut, imperdiet a, venenatis vitae, justo. Nullam dictum felis eu pede mollis pretium. Integer tincidunt. Cras dapibus. Vivamus elementum semper nisi. Aenean vulputate eleifend tellus. Aenean leo ligula, porttitor eu, consequat vitae, eleifend ac, enim. Aliquam lorem ante, dapibus in, viverra quis, feugiat a, tellus. Phasellus viverra nulla ut metus varius laoreet. Quisque rutrum. Aenean imperdiet. Etiam ultricies nisi vel augue. Curabitur ullamcorper ultricies nisi. Nam eget dui. Etiam rhoncus. Maecenas tempus, tellus eget condimentum rhoncus, sem quam semper libero, sit amet adipiscing sem neque sed ipsum. Nam quam nunc, blandit vel, luctus pulvinar, hendrerit id, lorem. Maecenas nec odio et ante tincidunt tempus. Donec vitae sapien ut libero venenatis faucibus. Nullam quis ante. Etiam sit amet orci eget eros faucibus tincidunt. Duis leo. Sed fringilla mauris sit amet nibh. Donec sodales sagittis magna. Sed consequat, leo eget bibendum sodales, augue velit cursus nunc, </div> <div id="wrapper"> <div id="blackBackground"></div> <canvas id="c"></canvas> </div> <script> var b = document.body; var c = document.getElementsByTagName('canvas')[0]; var a = c.getContext('2d'); document.body.clientWidth; // fix bug in webkit: http://qfox.nl/weblog/218 </script> 

Answer 1

將此添加到最后一個腳本標簽（在var c = ... ）：

var w = document.getElementById('wrapper');

那么您可以獲取並減去包裝偏移量屬性：

currentX = e.pageX - w.offsetLeft - c.offsetLeft - radiusPlusOffset || currentX;
currentY = e.pageY - w.offsetTop - c.offsetTop - radiusPlusOffset || currentY;