背景:我正在创建一个用于创建"低分辨率"显示。
现在我想用一个简单的演示来测试它 - 它应该在光标周围绘制一个径向渐变。
我认为我的数学正确并且它正常工作,除非您将鼠标移动到左下角。
我尝试打印数字,更改顺序等等,但无法找到原因。
这也是一个小提琴:https://jsfiddle.net/to5qfk7o/
var size = 16; // number of pixels
var lo = new Lores('#board', size, size);
// DRAWING FUNCTION
setInterval(function () {
// Mouse coords
var m_x = lo.mouse.x;
var m_y = lo.mouse.y;
// print where is mouse - for debug
console.log(m_x + "," + m_y);
// for all pixels on screen
for (var x = 0; x < size; x++) {
for (var y = 0; y < size; y++) {
// mouse distance from this pixel
var distance = (Math.sqrt((m_x - x) * (m_x - x) + (m_y - y) * (m_y - y)));
// convert: 0..255, "size"..0
var color = 255 - Math.floor((255 / size) * distance);
// set color
if (color < 0) {
lo.set(y, x, 'black');
} else {
lo.set(x, y, 'rgb(' + color + ', 0, 0)');
}
}
}
}, 100);
// ---- LIBRARY CODE -----
function Lores(selector, width, height) {
this.boardElem = document.querySelector(selector);
this.boardElem.className += ' lores-screen';
this.grid = [];
this.mouse = {
inside: false,
x: 0,
y: 0 // position rounded to nearest board "pixel"
};
this.width = width;
this.height = height;
if (this.boardElem === null) {
console.error('No such element!');
return;
}
if (width <= 0 || height <= 0) {
console.error('Dimensions must be positive!');
return;
}
// Inject a style block for the sizes
var css = selector + ' > div {height:' + (100 / height) + '%}';
css += selector + ' > div > div {width:' + (100 / width) + '%}';
var style = document.createElement('style');
style.type = 'text/css';
if (style.styleSheet) {
style.styleSheet.cssText = css;
} else {
style.appendChild(document.createTextNode(css));
}
document.head.appendChild(style);
var frag = document.createDocumentFragment();
// Create the grid
for (var i = height; i > 0; i--) {
var rowElem = document.createElement('div');
rowElem.dataset.y = i;
var row = [];
for (var j = width; j > 0; j--) {
var cellElem = document.createElement('div');
cellElem.dataset.x = j;
rowElem.appendChild(cellElem);
row.push(cellElem);
}
frag.appendChild(rowElem);
this.grid.push(row);
}
this.boardElem.appendChild(frag);
console.log('yo');
var self = this;
// add mouse listener
document.addEventListener('mousemove', function (e) {
var rect = self.boardElem.getBoundingClientRect();
var x = (self.width * (e.clientX - rect.left)) / rect.width;
var y = (self.height * (e.clientY - rect.top)) / rect.height;
self.mouse.x = Math.floor(x);
self.mouse.y = Math.floor(y);
self.mouse.inside = (x >= 0 && x < self.width && y >= 0 && y < self.height);
}, false);
}
Lores.prototype.set = function (x, y, color) {
if (x < 0 || x >= this.width || y < 0 || y >= this.height) return;
this.grid[y][x].style.backgroundColor = color;
};
&#13;
#board {
margin: 0 auto;
width: 128px;
height: 128px;
outline: 1px solid black;
}
#board > div:nth-child(odd) > div:nth-child(odd) {
background: #eee
}
#board > div:nth-child(even) > div:nth-child(even) {
background: #eee
}
.lores-screen {
display: block;
-webkit-touch-callout: none;
-webkit-user-select: none;
-khtml-user-select: none;
-moz-user-select: none;
-ms-user-select: none;
user-select: none;
}
.lores-screen, .lores-screen * {
white-space: nowrap;
padding: 0;
}
.lores-screen * {
margin: 0
}
.lores-screen > div {
display: block;
}
.lores-screen > div > div {
display: inline-block;
vertical-align: top;
height: 100%;
}
&#13;
<div id="board"></div>
&#13;
这可能是微不足道的,我真的不知道。谢谢!
答案 0 :(得分:10)
问题是if
声明中的简单拼写错误。您的x和y在第一个分支的set
中混淆了。话虽如此,我们可以完全消除分支。一个简单的Math.max(0, ...)
会将其默认为黑色。
更改以下内容:
var color = 255 - Math.floor((255 / size) * distance);
// set color
if (color < 0) {
lo.set(y, x, 'black');
} else {
lo.set(x, y, 'rgb(' + color + ', 0, 0)');
}
到
var color = Math.max(0, 255-Math.floor((255 / size) * distance));
lo.set(x, y, 'rgb(' + color + ', 0, 0)');
答案 1 :(得分:5)
变化
// set color
if (color < 0) {
lo.set(y, x, 'black');
} else {
lo.set(x, y, 'rgb(' + color + ', 0, 0)');
}
到
// set color
lo.set(x, y, 'rgb(' + Math.max(color, 0) + ', 0, 0)');