获取图像的平均外部像素颜色
问题描述:
所以我想获得图像中外部像素的平均颜色,以给出图像显示在div中的背景,颜色相同。所以我不必将所有图像都作为背景颜色。获取图像的平均外部像素颜色
示例:如果图像为100px x 100px
,则检查图像顶部的5个外部像素,图像右侧的5个外部像素,左侧和底部相同。您将获得5 x 100 x 4像素,获取颜色,检查平均值,并让JS为div分配相同的背景。
所以如果平均颜色是#000000
,div BG将是#000000
。如果平均值为#FAFAFA
,div BG将为#FAFAFA
答
您必须为此使用画布。这将需要CORS限制来实现。
如果这只是从要分析的区域中提取像素的问题,请合计并除以您计算的像素数。
演示
var img = new Image(); // load an image
img.crossOrigin = ""; // we need CORS here...
img.onload = function() { // when image has loaded:
var div = document.querySelector("div");
div.appendChild(this); // add image to DOM (demo)
div.style.background = analyse(img, 5); // bg color = result from analyse
}
img.src = "http://i.imgur.com/rUeQDjE.png"; // some image (CORS enabled)
function analyse(img, border) {
var canvas = document.createElement("canvas"), // create a canvas element
ctx = canvas.getContext("2d"), // get context
w = img.naturalWidth, // get actual width..
h = img.naturalHeight;
canvas.width = w; // set canvas size
canvas.height = h;
ctx.drawImage(img, 0, 0); // draw in image
// do checks:, for example:
//if (border*2 > canvas.width || border*2 > canvas.height) throw "Image too small!";
// get borders, avoid overlaps (though it does not really matter in this case):
var top = ctx.getImageData(0, 0, w, border).data;
var left = ctx.getImageData(0, border, border, h - border*2).data;
var right = ctx.getImageData(w - border, border, border, h - border*2).data;
var bottom = ctx.getImageData(0, h - border, w, border).data;
var r = 0, g = 0, b = 0, cnt = 0;
// count pixels and add up color components: (see function below)
countBuffer(top);
countBuffer(left);
countBuffer(right);
countBuffer(bottom);
// calc average
r = (r/cnt + 0.5)|0;
g = (g/cnt + 0.5)|0;
b = (b/cnt + 0.5)|0;
return "rgb(" + r + "," + g + "," + b + ")";
function countBuffer(data) {
var i = 0, len = data.length;
while(i < len) {
r += data[i++]; // add red component etc.
g += data[i++];
b += data[i++];
i++;
cnt++; // count one pixel
}
}
}
div {padding:30px}
<div></div>
+0
谢谢你帮助我,将在我的项目中使用它 – 2015-04-01 11:09:09
任何可用的代码? – roullie 2015-04-01 09:25:07