jquery - 有没有办法改变 jQuery flot 中绘图的颜色而不重新绘制整个图表？

Question

我有一个使用 flot 绘制的图表。当有人将鼠标悬停在文本上时，我想更改数据图的颜色。目前，我通过每次需要突出显示某些内容时重新绘制整个图表来实现此目的。这相当慢(简单的图表大约需要 30 毫秒，更复杂的图表则需要 100 毫秒)。由于我只想改变颜色，有没有更快的解决方案？

Answer 1

您可以立即采取措施来优化 Flot 的绘图流程。如果您不需要图表上的点，请将其关闭，这可以显着减少绘图时间。您还应该通过将 shadowSize 选项设置为 0 来关闭阴影，以提高速度。

除了这两项调整之外，您还必须更改 flot 源代码才能单独突出显示一个系列。我创建了一个完全可以做到这一点的补丁，以及一个小插件，可以让您自动或手动突出显示系列。该补丁和插件比重新绘制整个图表快三倍，它实际上还消除了取消突出显示一个系列所需的时间，因为它使用了flot的“覆盖”功能。

下面有一个 jquery.flot.js 补丁和 highlightSeries 插件的源代码，我创建了一个 demonstration page它可以让您看到各种设置以及补丁/插件组合之间的差异。

float 补丁

--- .\jquery.flot.js
+++ .\jquery.flot.js
@@ -147,6 +147,7 @@
         plot.setData = setData;
         plot.setupGrid = setupGrid;
         plot.draw = draw;
+        plot.drawSeries = drawSeries;
         plot.getPlaceholder = function() { return placeholder; };
         plot.getCanvas = function() { return canvas; };
         plot.getPlotOffset = function() { return plotOffset; };
@@ -164,6 +165,7 @@
         plot.highlight = highlight;
         plot.unhighlight = unhighlight;
         plot.triggerRedrawOverlay = triggerRedrawOverlay;
+        plot.drawOverlay = drawOverlay;
         plot.pointOffset = function(point) {
             return { left: parseInt(axisSpecToRealAxis(point, "xaxis").p2c(+point.x) + plotOffset.left),
                      top: parseInt(axisSpecToRealAxis(point, "yaxis").p2c(+point.y) + plotOffset.top) };
@@ -1059,7 +1061,7 @@
                 drawGrid();

             for (var i = 0; i < series.length; ++i)
-                drawSeries(series[i]);
+                drawSeries(series[i], ctx);

             executeHooks(hooks.draw, [ctx]);

@@ -1265,16 +1267,16 @@
             placeholder.append(html.join(""));
         }

-        function drawSeries(series) {
+        function drawSeries(series, ctx) {
             if (series.lines.show)
-                drawSeriesLines(series);
+                drawSeriesLines(series, ctx);
             if (series.bars.show)
-                drawSeriesBars(series);
+                drawSeriesBars(series, ctx);
             if (series.points.show)
-                drawSeriesPoints(series);
+                drawSeriesPoints(series, ctx);
         }

-        function drawSeriesLines(series) {
+        function drawSeriesLines(series, ctx) {
             function plotLine(datapoints, xoffset, yoffset, axisx, axisy) {
                 var points = datapoints.points,
                     ps = datapoints.pointsize,
@@ -1522,7 +1524,7 @@
             ctx.restore();
         }

-        function drawSeriesPoints(series) {
+        function drawSeriesPoints(series, ctx) {
             function plotPoints(datapoints, radius, fillStyle, offset, circumference, axisx, axisy) {
                 var points = datapoints.points, ps = datapoints.pointsize;

@@ -1675,7 +1677,7 @@
             }
         }

-        function drawSeriesBars(series) {
+        function drawSeriesBars(series, ctx) {
             function plotBars(datapoints, barLeft, barRight, offset, fillStyleCallback, axisx, axisy) {
                 var points = datapoints.points, ps = datapoints.pointsize;

@@ -1942,7 +1944,7 @@

                 if (hi.series.bars.show)
                     drawBarHighlight(hi.series, hi.point);
-                else
+                else if (hi.series.points.show)
                     drawPointHighlight(hi.series, hi.point);
             }
             octx.restore();

highlightSeries 插件

/*
Flot plugin for highlighting series.

    highlightSeries: {
        autoHighlight: true (default) or false
        , color: color
    }

If "autoHighlight" is true (the default) and the plot's "hoverable" setting is true
series are highlighted when the mouse hovers near an item.
"color" is the color of the highlighted series (default is "red").

The plugin also adds two public methods that allow you to highlight and
unhighlight a series manually by specifying a series by label, index or object.

    - highlightSeries(series, [color])

    - unHighlightSeries(series)
*/

(function ($) {
    var log = (function () {
        var out = $("#out");
        return function () {
            if (!arguments) { return; }
            var msg = Array.prototype.slice.call(arguments).join(" ");
            if (!out.length) {
                out = $("#out");
            }
            if (out.length) {
                out.text(msg);
            }
        };
    })();

    var options = {
        highlightSeries: {
            autoHighlight: true
            , color: "black"
            , _optimized: true
            , _debug: false
        }
    };

    function init(plot) {
        var highlightedSeries = {};
        var originalColors = {};

        function highlightSeries(series, color) {
            var
                seriesAndIndex = getSeriesAndIndex(series)
                , options = plot.getOptions().highlightSeries;

            series = seriesAndIndex[1];

            highlightedSeries[seriesAndIndex[0]] = series;
            originalColors[seriesAndIndex[0]] = series.color;

            series.color = color || options.color;

            if (options._debug) { var start = new Date(); }
            if (options._optimized) {
                if (plot.drawOverlay && options._debug) {
                    plot.drawOverlay();
                }
                else {
                    plot.triggerRedrawOverlay();
                }
            }
            else {
                plot.draw();
            }
            if (options._debug) { 
                log("Time taken to highlight:", (new Date()).getTime() - start.getTime(), "ms");
            }
        };
        plot.highlightSeries = highlightSeries;

        function unHighlightSeries(series) {
            var
                seriesAndIndex = getSeriesAndIndex(series)
                , options = plot.getOptions().highlightSeries;

            seriesAndIndex[1].color = originalColors[seriesAndIndex[0]];

            if (options._debug) { var start = new Date(); }
            if (options._optimized) {
                delete highlightedSeries[seriesAndIndex[0]];
                if (plot.drawOverlay && options._debug) {
                    plot.drawOverlay();
                }
                else {
                    plot.triggerRedrawOverlay();
                }
            }
            else {
                plot.draw();
            }
            if (options._debug) { 
                log("Time taken to un-highlight:", (new Date()).getTime() - start.getTime(), "ms");
            }
        };
        plot.unHighlightSeries = unHighlightSeries;

        plot.hooks.bindEvents.push(function (plot, eventHolder) {
            if (!plot.getOptions().highlightSeries.autoHighlight) {
                return;
            }

            var lastHighlighted = null;
            plot.getPlaceholder().bind("plothover", function (evt, pos, item) {
                if (item && lastHighlighted !== item.series) {
                    for(var seriesIndex in highlightedSeries) {
                        delete highlightedSeries[seriesIndex];
                    }
                    if (lastHighlighted) {
                        unHighlightSeries(lastHighlighted);
                    }
                    lastHighlighted = item.series;
                    highlightSeries(item.series);
                }
                else if (!item && lastHighlighted) {
                    unHighlightSeries(lastHighlighted);
                    lastHighlighted = null;
                }
            });
        });

        function getSeriesAndIndex(series) {
            var allPlotSeries = plot.getData();
            if (typeof series == "number") {
                return [series, allPlotSeries[series]];
            }
            else {
                for (var ii = 0; ii < allPlotSeries.length; ii++) {
                    var plotSeries = allPlotSeries[ii];
                    if (
                        plotSeries === series
                        || plotSeries.label === series
                        || plotSeries.label === series.label
                    ) {
                        return [ii, plotSeries];
                    }
                }
            }
        }

        plot.hooks.drawOverlay.push(function (plot, ctx) {
            for(var seriesIndex in highlightedSeries) {
                plot.drawSeries(highlightedSeries[seriesIndex], ctx);
            }
        });
    }

    $.plot.plugins.push({
        init: init,
        options: options,
        name: "highlightSeries",
        version: "1.0"
    });
})(jQuery);