网络办公正逐渐成为常态,无纸化办公也是一个潮流,这二者需要电子签章,最简单的方法就是在纸上盖一个章然后扫描成电子图片文件,最后在你的系统加载这个签章电子图片文件。但这样就会些不理想的地方,如果不是透明的,叠加在有文字等的地方会遮盖了原来的内容;如果做成透明的,图片会失真,看上去很不真实。
那就用代码画一个签章吧,本来以为是挺简单,其实不是。大小、形状、颜色这些都很受容易处理,难点就在文字按椭圆曲线排列上,涉及到字间距、倾斜角度等,实现起来还是要花一点时间的。
既然是要用代码来画,那就要用到 graphics 这个gdi了。为了画出高质量边缘无锯齿的透明图形,需要对graphics的绘画质量进行设置,并清除背景色。
image img = new bitmap(imgwidth, imgheight); graphics g = graphics.fromimage(img); g.smoothingmode = smoothingmode.highquality; g.interpolationmode = interpolationmode.highqualitybicubic; g.compositingquality = compositingquality.highquality; g.textrenderinghint = system.drawing.text.textrenderinghint.antialias; g.clear(color.transparent);
印章形状有圆形和椭圆形二种,圆形的话高和宽调成165的话打印出来和实际印章大小比较接近,椭圆形的宽和高则设置成197和131,当然在实际中是有不同大小的印章,只要调整宽和高就可。设置好宽和高后就可定义要画的图形大小和位置了,这里包含印章外边框和印章名称二个。
印章外边框的大小和位置
rectangle rect = new rectangle(new point(2, 2), new size(imgwidth - 5, imgheight - 5));
圆形印章名称的大小和位置
rectangle rectstring = new rectangle(new point(6, 6), new size(imgwidth - 12, imgheight - 12));
椭圆形印章名称的大小和位置
rectstring = new rectangle(new point(9, 9), new size(imgwidth - 16, imgheight - 16));
画印章外边框比较容易,直接画一个宽度为4的椭圆开就好了,圆形当椭圆一处理
g.drawellipse(new pen(forecolor, 4), rect);
还要确定印章中心点的坐标
point center = new point((imgwidth - 1) / 2, (imgheight - 1) / 2);
印章名称的绘画就复杂一点,为了文字的左右对称,需要设置绘画文字的起始角度、字间距和字体。实质上是把文字文字均匀地附加在圆形路径上。
public void drawellipsestring(rectangle rect, graphics g, font font, color forecolor, float startangle, string str, bool isfill, int split) { point origin = new point(rect.x + rect.width / 2, rect.y + rect.height / 2); stringformat format = new stringformat() { alignment = stringalignment.center, linealignment = stringalignment.center, }; if (rect.width == rect.height) { try { g.translatetransform(origin.x, origin.y); g.rotatetransform(startangle); float angle = startangle + 90; foreach (var c in str) { sizef txtsize = g.measurestring(c.tostring(), font); point pointb = getpiepoint(rect, angle); double distance = getrealdistance(origin, pointb); int radius = (int)(distance - txtsize.height / 2); pointf pointf = new pointf(0, -radius); g.drawstring(c.tostring(), font, new solidbrush(forecolor), pointf, format); float fltangle = 360f / str.length; if (!isfill) fltangle = (float)((txtsize.width + split - 2) / (rect.width * math.pi) * 360); g.rotatetransform(fltangle); angle += fltangle; } g.resettransform(); } catch { } } else { float angle = startangle - 90; sizef txtsize = g.measurestring(str.tostring(), font); rect = new rectangle(rect.x + (int)txtsize.height / 2, rect.y + (int)txtsize.height / 2, rect.width - (int)txtsize.height, rect.height - (int)txtsize.height); try { for (int i = 0; i < str.length; i++) { txtsize = g.measurestring(str[i].tostring(), font); point pointb = getpiepoint(rect, angle); double distance = getrealdistance(origin, pointb); g.translatetransform(pointb.x, pointb.y); if (angle == -90) { g.rotatetransform(angle + 90); } else if (angle == 0) { g.rotatetransform(angle + 90); } else if (angle == 90) { g.rotatetransform(angle + 90); } else if (angle == 180) { g.rotatetransform(angle + 90); } else if (angle == 270) { g.rotatetransform(angle + 90); } else if (angle == 360) { g.rotatetransform(angle - 45); } else { double a = rect.width / 2; double b = rect.height / 2; if (rect.height > rect.width) { a = rect.height / 2; b = rect.width / 2; } double c = math.sqrt(a * a - b * b); point f1 = new point((int)(origin.x - c), origin.y); point f2 = new point((int)(origin.x + c), origin.y); if (rect.height > rect.width) { f1 = new point(origin.x, (int)(origin.y - c)); f2 = new point(origin.x, (int)(origin.y + c)); } double pf1 = getrealdistance(f1, pointb); double pf2 = getrealdistance(f2, pointb); double f1f2 = getrealdistance(f1, f2); double pc = math.acos((distance * distance + pf2 * pf2 - c * c) / (2 * distance * pf2)) / math.pi * 180; if (angle > 270) pc = math.acos((distance * distance + pf1 * pf1 - c * c) / (2 * distance * pf1)) / math.pi * 180; if (angle < 90) pc = math.acos((distance * distance + pf1 * pf1 - c * c) / (2 * distance * pf1)) / math.pi * 180; if (pc.tostring() == "nan") pc = 0; double p = math.acos((pf1 * pf1 + pf2 * pf2 - f1f2 * f1f2) / (2 * pf1 * pf2)) / math.pi * 180; double q = p / 2 - pc; if (p < 0) q = 0; if (p == 0) q = 0; if (q.tostring() == "非数字") q = 0; if (q < 0) q = 0; float angleq = angleq = angle + 90 + (float)q; if (angle > 90 && angle < 180) angleq = angle + 90 - (float)q; if (angle > 270 && angle < 360) angleq = angle + 90 - (float)q; if (rect.height > rect.width) angleq = angle + 90 - (float)q; g.rotatetransform(angleq); } g.translatetransform(-pointb.x, -pointb.y); g.drawstring(str[i].tostring(), font, new solidbrush(forecolor), pointb, format); g.resettransform(); float fltangle = 360f / str.length; if (!isfill) { double stringwidth = txtsize.width + split - 2; for (float n = angle; n < 720; n += 0.1f) { point pointn = getpiepoint(rect, n); double stringn = getrealdistance(pointn, pointb); if (stringn > stringwidth) { fltangle = n - angle; break; } } } angle += fltangle; if (angle > 360) angle -= 360; } } catch { } } }
这里面要计算每一个文字的起始角度和坐标,还要计算二个点之间的距离
public point getpiepoint(rectangle lprect, float angle) { point pt = new point(); double a = lprect.width / 2.0f; double b = lprect.height / 2.0f; if (a == 0 || b == 0) return new point(lprect.x, lprect.y); //弧度 double radian = angle * math.pi / 180.0f; //获取弧度正弦值 double yc = math.sin(radian); //获取弧度余弦值 double xc = math.cos(radian); //获取曲率 r = ab/\sqrt((a.sinθ)^2+(b.cosθ)^2 double radio = (a * b) / math.sqrt(math.pow(yc * a, 2.0) + math.pow(xc * b, 2.0)); //计算坐标 double ax = radio * xc; double ay = radio * yc; pt.x = (int)(lprect.x + a + ax); pt.y = (int)(lprect.y + b + ay); return pt; } public double getrealdistance(point pointa, point pointb) { double distance = math.sqrt(math.pow(pointa.x - pointb.x, 2.0) + math.pow(pointa.y - pointb.y, 2.0)); return distance; }
印章中间的五角星形可以用特殊字符来做,但大小等的控制不如直接画线来得方便。
int radius = 27; pointf[] pentagons = new pointf[] { new pointf(center.x, center.y - radius), new pointf((float)(center.x + radius * math.sin(72 * math.pi / 180)), (float)(center.y - radius * math.cos(72 * math.pi / 180))), new pointf((float)(center.x + radius * math.sin(36 * math.pi / 180)), (float)(center.y + radius * math.cos(36* math.pi / 180))), new pointf((float)(center.x - radius * math.sin(36 * math.pi / 180)),(float)( center.y + radius * math.cos(36 * math.pi / 180))), new pointf((float)(center.x - radius * math.sin(72 * math.pi / 180)), (float)(center.y - radius * math.cos(72 * math.pi / 180))), }; graphicspath path = new graphicspath(fillmode.winding); path.addline(pentagons[0], pentagons[2]); path.addline(pentagons[2], pentagons[4]); path.addline(pentagons[4], pentagons[1]); path.addline(pentagons[1], pentagons[3]); path.addline(pentagons[3], pentagons[0]); path.closefigure(); g.fillpath(new solidbrush(forecolor), path);
印章的中间和底部文字相对简单,把字体设置小一点直接画就是,注意区分圆形和椭圆形。
if (showcenterstring) { if (isellipse) { g.drawstring(centerstring, new font(font.name, font.size - 1), new solidbrush(forecolor), center, format); } else { g.drawstring(centerstring, new font(font.name, font.size - 4), new solidbrush(forecolor), center, format); } } if (showbottomstring) { if (isellipse) { g.drawstring(bottomstring, new font(font.name, font.size - 1), new solidbrush(forecolor), center.x, center.y + 35, format); } else { g.drawstring(bottomstring, new font(font.name, font.size - 4), new solidbrush(forecolor), center.x, center.y + 50, format); } }
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