JavaScript绘图类 (DIV绘图)

主要的图形算法抄自一个叫w_jsGraphics.js的类库，第一次看到那个库的时候，感觉那是十分神奇的存在。
不过估计现在那个库早就已经找不到了.

这是很早之前的一个DIV绘图类，那时候VML+SVG的JS图库还没流行。

最初的神创造一个点，然后由这个点便画出一条线，最后这条线绘出了一个个世界。 

/**
 *JS 绘图类  Graphics- 0.02
 *@author  <a href="mailto: redrainyi@gmail.com">yao</a> *@param canvas 画布(画布可以是 DIV(IE) 或 Layer(Netscape)
 *参考资料《w_jsGraphics.js》《DHTML手册》《BISOFTJS》《Computer Graphics》
 *CopyLeft 2007 在引用或转载时请保持文件代码的完整性
 */
function Graphics(canvas)
{
	/*获得画板以后的绘图都是在画板上实现*/
	this.canvas = typeof(canvas)=="string"?document.getElementById(canvas):canvas;
	/*默认颜色 #000000黑色*/
	this.color = '#000000';
	/*设置线默认象素为 1px*/
	this.setStroke(1);
	/*文本默认字体*/
	this.setFont('verdana,geneva,helvetica,sans-serif', 20, "PLAIN");
	/*创建一个Div元素作为根结点 所有绘图的根结点*/
	this.documentRoot = document.createElement("div");
}
Graphics.prototype = {
	canvas : window,
	color  : '#000000',
	stroke : 1,
	documentRoot : null,
	/*设置颜色 格式"#RRGGBB" 颜色会保留到下一次再重新设置为止*/
	setColor : function(c)
	{
		this.color = c;
	},
	/*绘制点DIV*/
	drawDiv : function(x, y, w, h)
	{
		var elem = document.createElement("div");/*创建一个Div元素*/
		elem.style.position = 'absolute';
		elem.style.overflow = 'hidden';
		elem.style.left = x;
		elem.style.top  = y;
		elem.style.width  = w;
		elem.style.height = h ;
		elem.style.backgroundColor = this.color;
		this.documentRoot.appendChild(elem);
	},

	/*绘制组件 (绘图)*/
	paint : function()
	{
		this.canvas.appendChild(this.documentRoot);/*将根结点添加到画布上*/
	},

	/*清空画板*/
	clear : function()
	{
		if (this.canvas) this.canvas.innerHTML = '';
	},

	/*设置画笔 参数代表点(象素)大小 默认是 1px  (设置为-1时候代表 虚点线)*/
	setStroke : function(x)
	{
		this.stroke = x;
		if (!(x+1))	/*javaScript中 0为假 */
		{	/*设置画法为虚点*/
			this.drawLine = this.drawLineDott;
			this.drawOval = this.drawOvalDott;
			this.drawRect = this.drawRectangleDott;
		}
		else if (x > 1)
		{	/*实线*/
			this.drawLine = this.drawLine2D;
			this.drawOval = this.drawOval2D;
			this.drawRect = this.drawRectangle;
		}
		else
		{
			/*/象素大小(厚度)为1px的线*/
			this.drawLine = this.drawLine1D;
			this.drawOval = this.drawOval1D;
			this.drawRect = this.drawRectangle;
		}
	},

	/*画虚线*/
	drawLineDott : function(x1, y1, x2, y2)
	{
		if (x1 > x2)
		{
			var _x2 = x2;
			var _y2 = y2;
			x2 = x1;
			y2 = y1;
			x1 = _x2;
			y1 = _y2;
		}
		var dx = x2-x1, dy = Math.abs(y2-y1),
		x = x1, y = y1,
		yIncr = (y1 > y2)? -1 : 1,
		drw = true;
		if (dx >= dy)
		{
			var pr = dy<<1,
			pru = pr - (dx<<1),
			p = pr-dx;
			while ((dx--) > 0)
			{
				if (drw) this.drawDiv(x, y, 1, 1);
				drw = !drw;
				if (p > 0)
				{
					y += yIncr;
					p += pru;
				}
				else p += pr;
				++x;
			}
			if (drw) this.drawDiv(x, y, 1, 1);
		}
		else
		{
			var pr = dx<<1,
			pru = pr - (dy<<1),
			p = pr-dy;
			while ((dy--) > 0)
			{
				if (drw) this.drawDiv(x, y, 1, 1);
				drw = !drw;
				y += yIncr;
				if (p > 0)
				{
					++x;
					p += pru;
				}
				else p += pr;
			}
			if (drw) this.drawDiv(x, y, 1, 1);
		}
	},

	/*画线(经过优化的绘线方法)*/
	drawLine2D : function(x1, y1, x2, y2)
	{
		if (x1 > x2)
		{
			var _x2 = x2;
			var _y2 = y2;
			x2 = x1;
			y2 = y1;
			x1 = _x2;
			y1 = _y2;
		}
		var dx = x2-x1, dy = Math.abs(y2-y1),
		x = x1, y = y1,
		yIncr = (y1 > y2)? -1 : 1;

		var s = this.stroke;
		if (dx >= dy)
		{
			if (dx > 0 && s-3 > 0)
			{
				var _s = (s*dx*Math.sqrt(1+dy*dy/(dx*dx))-dx-(s>>1)*dy) / dx;
				_s = (!(s-4)? Math.ceil(_s) : Math.round(_s)) + 1;
			}
			else var _s = s;
			var ad = Math.ceil(s/2);

			var pr = dy<<1,
			pru = pr - (dx<<1),
			p = pr-dx,
			ox = x;
			while ((dx--) > 0)
			{
				++x;
				if (p > 0)
				{
					this.drawDiv(ox, y, x-ox+ad, _s);
					y += yIncr;
					p += pru;
					ox = x;
				}
				else p += pr;
			}
			this.drawDiv(ox, y, x2-ox+ad+1, _s);
		}else{
			if (s-3 > 0)
			{
				var _s = (s*dy*Math.sqrt(1+dx*dx/(dy*dy))-(s>>1)*dx-dy) / dy;
				_s = (!(s-4)? Math.ceil(_s) : Math.round(_s)) + 1;
			}
			else var _s = s;
			var ad = Math.round(s/2);

			var pr = dx<<1,
			pru = pr - (dy<<1),
			p = pr-dy,
			oy = y;
			if (y2 <= y1)
			{
				++ad;
				while ((dy--) > 0)
				{
					if (p > 0)
					{
						this.drawDiv(x++, y, _s, oy-y+ad);
						y += yIncr;
						p += pru;
						oy = y;
					}
					else
					{
						y += yIncr;
						p += pr;
					}
				}
				this.drawDiv(x2, y2, _s, oy-y2+ad);
			}
			else
			{
				while ((dy--) > 0)
				{
					y += yIncr;
					if (p > 0)
					{
						this.drawDiv(x++, oy, _s, y-oy+ad);
						p += pru;
						oy = y;
					}
					else p += pr;
				}
				this.drawDiv(x2, oy, _s, y2-oy+ad+1);
			}
		}
	},

	/*画线(象素大小为1的线 参考Bresenham算法)*/
	drawLine1D : function(x1, y1, x2, y2)
	{
		if (x1 > x2)
		{
			var _x2 = x2;
			var _y2 = y2;
			x2 = x1;
			y2 = y1;
			x1 = _x2;
			y1 = _y2;
		}
		var dx = x2-x1, dy = Math.abs(y2-y1),
		x = x1, y = y1,
		yIncr = (y1 > y2)? -1 : 1;

		if (dx >= dy)
		{
			var pr = dy<<1,
			pru = pr - (dx<<1),
			p = pr-dx,
			ox = x;
			while ((dx--) > 0)
			{
				++x;
				if (p > 0)
				{
					this.drawDiv(ox, y, x-ox, 1);
					y += yIncr;
					p += pru;
					ox = x;
				}
				else p += pr;
			}
			this.drawDiv(ox, y, x2-ox+1, 1);
		}
		else
		{
			var pr = dx<<1,
			pru = pr - (dy<<1),
			p = pr-dy,
			oy = y;
			if (y2 <= y1)
			{
				while ((dy--) > 0)
				{
					if (p > 0)
					{
						this.drawDiv(x++, y, 1, oy-y+1);
						y += yIncr;
						p += pru;
						oy = y;
					}
					else
					{
						y += yIncr;
						p += pr;
					}
				}
				this.drawDiv(x2, y2, 1, oy-y2+1);
			}
			else
			{
				while ((dy--) > 0)
				{
					y += yIncr;
					if (p > 0)
					{
						this.drawDiv(x++, oy, 1, y-oy);
						p += pru;
						oy = y;
					}
					else p += pr;
				}
				this.drawDiv(x2, oy, 1, y2-oy+1);
			}
		}
	},

	/*圆弧 八个对称点的算法*/
	drawCirclePoints : function(cx, cy, xl, xr, yt, yb, w, h)
	{
		this.drawDiv(xr+cx, yt+cy, w, h);
		this.drawDiv(xr+cx, yb+cy, w, h);
		this.drawDiv(xl+cx, yb+cy, w, h);
		this.drawDiv(xl+cx, yt+cy, w, h);
	},

	/*圆形(椭圆形 卵形)*/
	drawOval2D : function(left, top, width, height)
	{
		var s = this.stroke;
		width += s-1;
		height += s-1;
		var a = width>>1, b = height>>1,
		wod = width&1, hod = (height&1)+1,
		cx = left+a, cy = top+b,
		x = 0, y = b,
		aa = (a*a)<<1, bb = (b*b)<<1,
		st = (aa>>1)*(1-(b<<1)) + bb,
		tt = (bb>>1) - aa*((b<<1)-1);

		if (s-4 < 0 && (!(s-2) || width-51 > 0 && height-51 > 0))
		{
			var ox = 0, oy = b,
			w, h,
			pxl, pxr, pxt, pxb, pxw;
			while (y > 0)
			{
				if (st < 0)
				{
					st += bb*((x<<1)+3);
					tt += (bb<<1)*(++x);
				}
				else if (tt < 0)
				{
					st += bb*((x<<1)+3) - (aa<<1)*(y-1);
					tt += (bb<<1)*(++x) - aa*(((y--)<<1)-3);
					w = x-ox;
					h = oy-y;

					if (w-1)
					{
						pxw = w+1+(s&1);
						h = s;
					}
					else if (h-1)
					{
						pxw = s;
						h += 1+(s&1);
					}
					else pxw = h = s;
					this.drawCirclePoints(cx, cy, -x+1, ox-pxw+w+wod, -oy, -h+oy+hod, pxw, h);
					ox = x;
					oy = y;
				}
				else
				{
					tt -= aa*((y<<1)-3);
					st -= (aa<<1)*(--y);
				}
			}
			this.drawDiv(cx-a, cy-oy, s, (oy<<1)+hod);
			this.drawDiv(cx+a+wod-s+1, cy-oy, s, (oy<<1)+hod);
		}
		else
		{
			var _a = (width-((s-1)<<1))>>1,
			_b = (height-((s-1)<<1))>>1,
			_x = 0, _y = _b,
			_aa = (_a*_a)<<1, _bb = (_b*_b)<<1,
			_st = (_aa>>1)*(1-(_b<<1)) + _bb,
			_tt = (_bb>>1) - _aa*((_b<<1)-1),

			pxl = new Array(),
			pxt = new Array(),
			_pxb = new Array();
			pxl[0] = 0;
			pxt[0] = b;
			_pxb[0] = _b-1;
			while (y > 0)
			{
				if (st < 0)
				{
					st += bb*((x<<1)+3);
					tt += (bb<<1)*(++x);
					pxl[pxl.length] = x;
					pxt[pxt.length] = y;
				}
				else if (tt < 0)
				{
					st += bb*((x<<1)+3) - (aa<<1)*(y-1);
					tt += (bb<<1)*(++x) - aa*(((y--)<<1)-3);
					pxl[pxl.length] = x;
					pxt[pxt.length] = y;
				}
				else
				{
					tt -= aa*((y<<1)-3);
					st -= (aa<<1)*(--y);
				}

				if (_y > 0)
				{
					if (_st < 0)
					{
						_st += _bb*((_x<<1)+3);
						_tt += (_bb<<1)*(++_x);
						_pxb[_pxb.length] = _y-1;
					}
					else if (_tt < 0)
					{
						_st += _bb*((_x<<1)+3) - (_aa<<1)*(_y-1);
						_tt += (_bb<<1)*(++_x) - _aa*(((_y--)<<1)-3);
						_pxb[_pxb.length] = _y-1;
					}
					else
					{
						_tt -= _aa*((_y<<1)-3);
						_st -= (_aa<<1)*(--_y);
						_pxb[_pxb.length-1]--;
					}
				}
			}

			var ox = 0, oy = b,
			_oy = _pxb[0],
			l = pxl.length,
			w, h;
			for (var i = 0; i < l; i++)
			{
				if (typeof _pxb[i] != "undefined")
				{
					if (_pxb[i] < _oy || pxt[i] < oy)
					{
						x = pxl[i];
						this.drawCirclePoints(cx, cy, -x+1, ox+wod, -oy, _oy+hod, x-ox, oy-_oy);
						ox = x;
						oy = pxt[i];
						_oy = _pxb[i];
					}
				}
				else
				{
					x = pxl[i];
					this.drawDiv(cx-x+1, cy-oy, 1, (oy<<1)+hod);
					this.drawDiv(cx+ox+wod, cy-oy, 1, (oy<<1)+hod);
					ox = x;
					oy = pxt[i];
				}
			}
			this.drawDiv(cx-a, cy-oy, 1, (oy<<1)+hod);
			this.drawDiv(cx+ox+wod, cy-oy, 1, (oy<<1)+hod);
		}
	},

	/*线象素为1 的圆形*/
	drawOval1D : function(x1, y1, w1, h1)
	{
		var a = w1>>1, b = h1>>1,
		wod = w1&1, hod = (h1&1)+1,
		cx = x1+a, cy = y1+b,
		x = 0, y = b,
		ox = 0, oy = b,
		aa = (a*a)<<1, bb = (b*b)<<1,
		st = (aa>>1)*(1-(b<<1)) + bb,
		tt = (bb>>1) - aa*((b<<1)-1),
		w, h;
		while (y > 0)
		{
			if (st < 0)
			{
				st += bb*((x<<1)+3);
				tt += (bb<<1)*(++x);
			}
			else if (tt < 0)
			{
				st += bb*((x<<1)+3) - (aa<<1)*(y-1);
				tt += (bb<<1)*(++x) - aa*(((y--)<<1)-3);
				w = x-ox;
				h = oy-y;
				if (w&2 && h&2)
				{
					this.drawCirclePoints(cx, cy, -x+2, ox+wod, -oy, oy-1+hod, 1, 1);
					this.drawCirclePoints(cx, cy, -x+1, x-1+wod, -y-1, y+hod, 1, 1);
				}
				else this.drawCirclePoints(cx, cy, -x+1, ox+wod, -oy, oy-h+hod, w, h);
				ox = x;
				oy = y;
			}
			else
			{
				tt -= aa*((y<<1)-3);
				st -= (aa<<1)*(--y);
			}
		}
		this.drawDiv(cx-a, cy-oy, a-ox+1, (oy<<1)+hod);
		this.drawDiv(cx+ox+wod, cy-oy, a-ox+1, (oy<<1)+hod);
	},

	/*虚点圆形*/
	drawOvalDott : function(x1, y1, w1, h1)
	{
		var a = w1>>1, b = h1>>1,
		wod = w1&1, hod = h1&1,
		cx = x1+a, cy = y1+b,
		x = 0, y = b,
		aa2 = (a*a)<<1, aa4 = aa2<<1, bb = (b*b)<<1,
		st = (aa2>>1)*(1-(b<<1)) + bb,
		tt = (bb>>1) - aa2*((b<<1)-1),
		drw = true;
		while (y > 0)
		{
			if (st < 0)
			{
				st += bb*((x<<1)+3);
				tt += (bb<<1)*(++x);
			}
			else if (tt < 0)
			{
				st += bb*((x<<1)+3) - aa4*(y-1);
				tt += (bb<<1)*(++x) - aa2*(((y--)<<1)-3);
			}
			else
			{
				tt -= aa2*((y<<1)-3);
				st -= aa4*(--y);
			}
			if (drw) this.drawCirclePoints(cx, cy, -x, x+wod, -y, y+hod, 1, 1);
			drw = !drw;
		}
	},

	/*绘制矩形(边为虚线的矩形)*/
	drawRectangleDott : function(x, y, w, h)
	{
		this.drawLine(x, y, x+w, y);
		this.drawLine(x+w, y, x+w, y+h);
		this.drawLine(x, y+h, x+w, y+h);
		this.drawLine(x, y, x, y+h);
	},

	/*绘制矩形(边为实线的矩形)*/
	drawRectangle : function(x, y, w, h)
	{
		var s = this.stroke;
		this.drawDiv(x, y, w, s);
		this.drawDiv(x+w, y, s, h);
		this.drawDiv(x, y+h, w+s, s);
		this.drawDiv(x, y+s, s, h-s);
	},

	/*绘制折线 参数是每个点xy轴坐标数祖集合*/
	drawPolyLine : function(xPoints, yPoints)
	{
		for (var i=0 ; i<xPoints.length-1 ; i++ )
		{
			this.drawLine(xPoints[i], yPoints[i], xPoints[i+1], yPoints[i+1]);
		};
	},

	/*填充图形部分*/

	/*填充矩形*/
	fillRect : function(x, y, w, h)
	{
		this.drawDiv(x, y, w, h);
	},

	/*多边形 与折线类似不同的地方是多边形是闭合的*/
	drawPolygon : function(xPoints, yPoints)
	{
		this.drawPolyline(xPoints, yPoints);
		this.drawLine(xPoints[x.length-1], yPoints[x.length-1], x[0], y[0]);
	},

	/*填充的圆形(椭圆形)*/
	fillOval : function(left, top, w, h)
	{
		var a = (w -= 1)>>1, b = (h -= 1)>>1,
		wod = (w&1)+1, hod = (h&1)+1,
		cx = left+a, cy = top+b,
		x = 0, y = b,
		ox = 0, oy = b,
		aa2 = (a*a)<<1, aa4 = aa2<<1, bb = (b*b)<<1,
		st = (aa2>>1)*(1-(b<<1)) + bb,
		tt = (bb>>1) - aa2*((b<<1)-1),
		pxl, dw, dh;
		if (w+1) while (y > 0)
		{
			if (st < 0)
			{
				st += bb*((x<<1)+3);
				tt += (bb<<1)*(++x);
			}
			else if (tt < 0)
			{
				st += bb*((x<<1)+3) - aa4*(y-1);
				pxl = cx-x;
				dw = (x<<1)+wod;
				tt += (bb<<1)*(++x) - aa2*(((y--)<<1)-3);
				dh = oy-y;
				this.drawDiv(pxl, cy-oy, dw, dh);
				this.drawDiv(pxl, cy+y+hod, dw, dh);
				ox = x;
				oy = y;
			}
			else
			{
				tt -= aa2*((y<<1)-3);
				st -= aa4*(--y);
			}
		}
		this.drawDiv(cx-a, cy-oy, w+1, (oy<<1)+hod);
	},

	/**
	 *填充的多边形 参数 x坐标数组 y坐标数组
	 *数组示例：
	 *var Xpoints = new Array(10,80,80,50);
	 *var YPoints = new Array(50,10,90,80);
	 *jg.drawPolyline(Xpoints,Ypoints);
	 */
	fillPolygon : function(array_x, array_y)
	{
		var i;
		var y;
		var miny, maxy;
		var x1, y1;
		var x2, y2;
		var ind1, ind2;
		var ints;

		var n = array_x.length;	/*数组长度 正常输入的情况 array_x.length == array_y.length;*/

		if (!n) return;		/*如果输入数组为空 直接返回*/

		/*得到最大于最小的y坐标*/
		miny = array_y[0];
		maxy = array_y[0];
		for (i = 1; i < n; i++)
		{
			if (array_y[i] < miny)
				miny = array_y[i];

			if (array_y[i] > maxy)
				maxy = array_y[i];
		}

		/*最小Y坐标 -> 最大Y坐标*/
		for (y = miny; y <= maxy; y++)
		{
			var polyInts = new Array();
			ints = 0;
			/*参数数组 -> */
			for (i = 0; i < n; i++)
			{
				if (!i)		// if( i != 0)
				{
					ind1 = n-1;
					ind2 = 0;
				}
				else
				{
					ind1 = i-1;
					ind2 = i;
				}
				y1 = array_y[ind1];
				y2 = array_y[ind2];
				if (y1 < y2)
				{
					x1 = array_x[ind1];
					x2 = array_x[ind2];
				}
				else if (y1 > y2)
				{
					y2 = array_y[ind1];
					y1 = array_y[ind2];
					x2 = array_x[ind1];
					x1 = array_x[ind2];
				}
				else continue;

				if ((y >= y1) && (y < y2))
					polyInts[ints++] = Math.round((y-y1) * (x2-x1) / (y2-y1) + x1);

				else if ((y == maxy) && (y > y1) && (y <= y2))
					polyInts[ints++] = Math.round((y-y1) * (x2-x1) / (y2-y1) + x1);
			}

			/*sort函数:默认根据ASCII升序排列,这里使用用函数(integer_compare)来确定元素顺序*/
			polyInts.sort(new Function('x,y', 'return (x < y) ? -1 : ((x > y)*1);'));

			for (i = 0; i < ints; i+=2)
				this.drawDiv(polyInts[i], y, polyInts[i+1]-polyInts[i]+1, 1);
		}
	},

	/*文本 参数为x y坐标 文本字符串*/
	drawString : function(txt, x, y)
	{
		var elem = document.createElement("div");
		elem.style.position = 'absolute';
		elem.style.overflow = 'hidden';
		elem.style.left = x ;
		elem.style.top  = y ;
		/*elem.style.backgroundColor = this.color;*/
		elem.style.fontFamily = this.fFamily;
		elem.style.fontSize   = this.fSize;
		elem.style.color      = this.color;

		/*字体属性*/
		if(this.fStyle=="PLAIN"){
			elem.style.fontweight = 'normal';/*默认字体*/
		}else if(this.fStyle=="ITALIC"){
			elem.style.fontweight = 'bold';/*斜体字*/
		}else if(this.fStyle=="BOLD"){
			elem.style.fontStyle  = 'italic';/*斜体字*/
		}else if(this.fStyle=="ITALIC_BOLD"){
			elem.style.fontweight = 'bold';/*粗体字*/
			elem.style.fontStyle  = 'italic';/*斜体字*/
		}else if((this.fStyle=="BOLD_ITALIC")){
			elem.style.fontStyle  = 'italic';/*斜体字*/
			elem.style.fontweight = 'bold';/*粗体字*/
		}else{
			elem.style.fontweight = 'normal';/*默认字体PLAIN*/
		}
		elem.appendChild(document.createTextNode(txt));
		this.documentRoot.appendChild(elem);
	},

	/**设置字体
	 * 参数:(字形 尺寸 样式)
	 * 尺寸:(单位象素)
	 * 样式:(PLAIN 默认,BOLD 粗体,ITALIC 斜体,ITALIC_BOLD 斜粗体,BOLD_ITALIC 粗斜体)
	 */
	setFont : function(fFamily, fSize, fStyle)
	{
		this.fFamily = fFamily;
		this.fSize   = fSize;
		this.fStyle  = fStyle;
	},

	/*添加图片 图片地址 位置宽高*/
	drawImage : function(imgSrc, x, y, w, h)
	{
		var elem = document.createElement("div");
		elem.style.position = 'absolute';
		elem.style.overflow = 'hidden';
		elem.style.left  = x ;
		elem.style.top   = y ;
		elem.style.width = w ;
		elem.style.height= h ; 

		var elemImg = document.createElement("img");
		elemImg.src = imgSrc;
		elemImg.style.left  = x ;
		elemImg.style.top   = y ;
		elemImg.style.width = w ;
		elemImg.style.height= h ;

		elem.appendChild(elemImg);
		this.documentRoot.appendChild(elem);
	}
};

甚以此纪念充满激情的岁月。