本文参考博客：http://blog.csdn.net/heyzol/article/details/22912389

由于我是固定了刻度数，美观的呈现图表，所以在原博主算法上进行了修改

var calculateRulerMark = function(arrMark, numMin, numMax, iHeight, iActualMarkNum)
{if(numMax <= numMin){return; }var iMinMark = numMin;var iMaxMark = numMax;var iSuggestMarkNum = parseInt(iHeight / 20) + 1;//传了实际的进来说明，实际的比建议的大iActualMarkNum = iActualMarkNum ? iActualMarkNum - 1 : iSuggestMarkNum;var iSuggestStep = (numMax - numMin) / iActualMarkNum;var iBase = Math.pow(10, parseInt(Math.log(iSuggestStep)/Math.log(10)));if(iBase != iSuggestStep){iBase = 10 * iBase;}var iTempStep = (iSuggestStep / iBase).toFixed(6);// 常规步长 0.1, 0.2, 0.25, 0.5 , 1 if(iTempStep >= 0 && iTempStep <= 0.1){iTempStep = 0.1;}else if(iTempStep >=0.100001 && iTempStep <= 0.2){iTempStep = 0.2;}else if(iTempStep >= 0.200001 && iTempStep <= 0.25){iTempStep = 0.25;}else if(iTempStep >= 0.250001 && iTempStep <= 0.5){iTempStep = 0.5}else{iTempStep = 1;}iTempStep = iTempStep * iBase;//判断最小刻度是否需要+1if(parseInt(numMin / iTempStep) != numMin / iTempStep){if(numMin < 0){iMinMark = (-1) * Math.ceil(Math.abs(numMin/iTempStep))*iTempStep;}else{iMinMark = parseInt(Math.abs(numMin/iTempStep))*iTempStep;}}//判断最大刻度是否需要+1if(parseInt(numMax / iTempStep) != numMax / iTempStep){if(numMax < 0){iMaxMark = (-1) * Math.floor(Math.abs(numMax/iTempStep))*iTempStep;}else{iMaxMark = parseInt(numMax/iTempStep + 1)*iTempStep;}}var iTempMarkNum = (iMaxMark - iMinMark) / iTempStep + 1;if(iTempMarkNum > iSuggestMarkNum){calculateRulerMark(arrMark, numMin, numMax, iHeight, iActualMarkNum)}else{iSuggestMarkNum = iTempMarkNum;for(var i = 0; i < iSuggestMarkNum; i++){arrMark.push(iMinMark+ iTempStep * i);}}
}