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Image intensity histogram
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| <!doctype html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <style> | |
| body { | |
| font: 10px sans-serif; | |
| } | |
| #main { | |
| position: relative; | |
| width: 634px; | |
| margin: auto; | |
| } | |
| canvas { | |
| padding: 0; | |
| margin: 0; | |
| } | |
| svg { | |
| position: absolute; | |
| top: 0; | |
| bottom: 0; | |
| } | |
| .brush .extent { | |
| fill-opacity: .3; | |
| shape-rendering: crispEdges; | |
| } | |
| .resize rect { | |
| visibility: visible !important; | |
| fill: #333; | |
| fill-opacity: .8; | |
| stroke: #555; | |
| stroke-width: 1.5px; | |
| } | |
| .histo { | |
| fill-opacity: .4; | |
| stroke-width: 2; | |
| } | |
| </style> | |
| <title></title> | |
| </head> | |
| <body> | |
| <div id="main"></div> | |
| <script> | |
| 'use strict'; | |
| function load() { | |
| var image = this, | |
| width = image.width, | |
| height = image.height, | |
| data = [], | |
| brushsize = 6, | |
| x = d3.scale.linear().range([0, width - brushsize]), | |
| y = d3.scale.linear().range([brushsize, height - brushsize]), | |
| rgb = d3.scale.ordinal().domain(d3.range(3)).range(["red", "green", "blue"]), | |
| xH = d3.scale.linear().domain([0, 255]).range([0, width]), | |
| yH = d3.scale.linear().range([0, height / 4]); | |
| var svg, canvas, histo; | |
| var empty = Array(256); | |
| for (var i = 0; i < 256; i++) { empty[i] = 0; } | |
| function histogram(extent, context) { | |
| var x = width * extent[0][0], | |
| y = height * extent[0][1], | |
| w = width * (extent[1][0] - extent[0][0]), | |
| h = height * (extent[1][1] - extent[0][1]), | |
| p = context.getImageData(x, y, w, h).data, | |
| d = d3.range(3).map(function() { | |
| return empty.slice(); | |
| }); | |
| i = 0; | |
| do { | |
| d[0][p[i++]]++; | |
| d[1][p[i++]]++; | |
| d[2][p[i++]]++; | |
| i++; // alpha | |
| } while(i < p.length) | |
| var max = Math.max(d3.max(d[0]), d3.max(d[1]), d3.max(d[2])); | |
| yH.domain([0, max]); | |
| return d; | |
| } | |
| function brushmove() { | |
| canvas.each(function() { | |
| data = histogram(brush.extent(), this.context); | |
| redraw(); | |
| }); | |
| } | |
| function draw() { | |
| histo = svg.selectAll(".histo") | |
| .data(data).enter() | |
| .append("path") | |
| .attr("class", "histo") | |
| .attr("fill", function(d, i) { return rgb(i); }) | |
| .attr("stroke", function(d, i) { return rgb(i); }); | |
| redraw(); | |
| } | |
| function redraw() { | |
| histo.data(data).attr("d", area); | |
| } | |
| var area = d3.svg.area() | |
| .x(function(d, i) { return xH(i); }) | |
| .y0(height) | |
| .y1(function(d) { return height - yH(d); }) | |
| .interpolate("basis"); | |
| var brush = d3.svg.brush() | |
| .x(x) | |
| .y(y) | |
| .extent([[.4, .4],[.6, .6]]) | |
| .on("brush", brushmove); | |
| svg = d3.select("#main") | |
| .append("svg") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .append("g") | |
| canvas = d3.select("#main") | |
| .append("canvas") | |
| .attr("width", width) | |
| .attr("height", height) | |
| .each(function() { | |
| this.context = this.getContext('2d'); | |
| this.context.drawImage(image, 0, 0); | |
| data = histogram(brush.extent(), this.context); | |
| draw(); | |
| }); | |
| svg.append("g") | |
| .attr("class", "brush") | |
| .call(brush); | |
| } | |
| document.addEventListener('DOMContentLoaded', function() { | |
| var image = new Image(); | |
| image.src = 'l.jpg'; | |
| image.addEventListener("load", load); | |
| }); | |
| </script> | |
| </body> | |
| </html> |
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