引言

在PDF中我们可以通过C#程序代码来添加非常丰富的元素来呈现我们想要表达的内容,如绘制表格、文字,添加图形、图像等等。在本篇文章中,我将介绍如何在PDF中绘制图形,并设置图形属性的操作。

文章中将分以下要点进行介绍:

  1. 绘制基本图形(线条、椭圆、圆形、矩形、三角形)
  2. 绘制自定义图形
  3. 绘制图形并设置图形透明度
    所需工具Spire.PDF for .NET 4.0

提示:安装后,直接引用安装路径下Bin文件夹中的dll文件到项目程序中即可。

【示例1】绘制基本图形

步骤1:新建一个PDF文档,添加页,添加画笔、画刷

           //新建一个PDF文档,添加页
            PdfDocument doc = new PdfDocument();
            PdfPageBase page = doc.Pages.Add();

            //设置画笔和画刷
            PdfPen pen = new PdfPen(PdfBrushes.Black, 1f);
            PdfBrush brush1 = PdfBrushes.RosyBrown;
            PdfBrush brush2 = PdfBrushes.Goldenrod;

步骤2:绘制圆形、矩形、线段、三角形

            //绘入矩形(此处通过设置值来绘制成正方形)
            page.Canvas.DrawRectangle(pen, brush1, new Rectangle(new Point(50, 50), new Size(60, 60)));

            //绘入椭圆(此处通过设置值来绘制成圆形)
            page.Canvas.DrawEllipse(pen, brush2, 210, 50, 60, 60);

            //绘入线段
            page.Canvas.DrawLine(pen, new PointF(50, 115), new PointF(270, 115));

            //绘入多边形(此处绘制成三角形)
            PointF p1 = new PointF(130, 172);
            PointF p2 = new PointF(160, 120);
            PointF p3 = new PointF(190, 172);
            PointF[] points = new PointF[] { p1, p2, p3 };
            page.Canvas.DrawPolygon(pen, points);

步骤3:保存文档

            //保存并打开文档
            doc.SaveToFile("基本图形.pdf");
            System.Diagnostics.Process.Start("基本图形.pdf");

图形添加效果:
C# 绘制PDF图形——基本图形、自定义图形、色彩透明度

【示例2】绘制自定义图形

步骤1:创建pdf文档,调用方法DrawStar()绘制自定义图形,并保存

            //新建一个PDF文档,添加页
            PdfDocument doc = new PdfDocument();
            PdfPageBase page = doc.Pages.Add();

            //调用DrawStar()方法绘入五角星图形
            DrawStar(page);

            //保存并打开文档
            doc.SaveToFile("自定义图形.pdf");
            System.Diagnostics.Process.Start("自定义图形.pdf");

步骤2:自定义DrawStar()方法绘制几个不同样式的五角星

private static void DrawStar(PdfPageBase page)
        {
            //设置五角星的5个顶点坐标
            PointF[] points = new PointF[5];
            for (int i = 0; i < points.Length; i++)
            {
                float x = (float)Math.Cos(i * 2 * Math.PI / 5);
                float y = (float)Math.Sin(i * 2 * Math.PI / 5);
                points[i] = new PointF(x, y);
            }

            //创建PdfPath类,在顶点之间添加线段组成五角星
            PdfPath path = new PdfPath();
            path.AddLine(points[2], points[0]);
            path.AddLine(points[0], points[3]);
            path.AddLine(points[3], points[1]);
            path.AddLine(points[1], points[4]);
            path.AddLine(points[4], points[2]);

            //保存画布状态
            PdfGraphicsState state = page.Canvas.Save();

            //实例化画笔和画刷1、画刷2
            PdfPen pen = new PdfPen(Color.DeepSkyBlue, 0.02f);
            PdfBrush brush1 = new PdfSolidBrush(Color.PaleGreen);
            PdfBrush brush2 = new PdfSolidBrush(Color.Bisque);
            //将坐标放大40倍
            page.Canvas.ScaleTransform(40f, 40f);

            //平移坐标
            page.Canvas.TranslateTransform(1f, 1.5f);

            //绘入第一个五角星
            page.Canvas.DrawPath(pen, path);

            //平移坐标并在新的位置绘入第二个五角星
            page.Canvas.TranslateTransform(2f, 0f);
            path.FillMode = PdfFillMode.Alternate;
            page.Canvas.DrawPath(pen, brush1, path);

            //平移坐标并在新的位置绘入第三个五角星
            page.Canvas.TranslateTransform(2f, 0f);
            path.FillMode = PdfFillMode.Winding;
            page.Canvas.DrawPath(pen, brush2, path);

            //实例化画刷3,平移坐标并在新的位置绘入第四个五角星
            PdfLinearGradientBrush brush3
                = new PdfLinearGradientBrush(new PointF(-2, 0), new PointF(2, 0), Color.OrangeRed, Color.Yellow);
            page.Canvas.TranslateTransform(-4f, 2f);
            path.FillMode = PdfFillMode.Alternate;
            page.Canvas.DrawPath(pen, brush3, path);

            //实例化画刷4,平移坐标并在新的位置绘入第五个五角星
            PdfRadialGradientBrush brush4
                = new PdfRadialGradientBrush(new PointF(0f, 0f), 0f, new PointF(0f, 0f), 1f, Color.Orchid, Color.LightBlue);
            page.Canvas.TranslateTransform(2f, 0f);
            path.FillMode = PdfFillMode.Winding;
            page.Canvas.DrawPath(pen, brush4, path);

            //实例化画刷5,平移坐标并在新的位置绘入第六个五角星
            PdfTilingBrush brush5 = new PdfTilingBrush(new RectangleF(0, 0, 4f, 4f));
            brush5.Graphics.DrawRectangle(brush3, 0, 0, 4f, 4f);
            page.Canvas.TranslateTransform(2f, 0f);
            path.FillMode = PdfFillMode.Winding;
            page.Canvas.DrawPath(pen, brush5, path);

            //再次保存画布状态
            page.Canvas.Restore(state);
        }

自定义图形添加效果:

C# 绘制PDF图形——基本图形、自定义图形、色彩透明度

【示例3】设置色彩透明度

步骤1:新建一个PDF文档,添加页

            PdfDocument doc = new PdfDocument();
            PdfPageBase page = doc.Pages.Add();

步骤2:初始化一个PdfSeparationColorSpace的对象,用于创建基本色,并将基本色透明度设置为1

             PdfSeparationColorSpace cs1 = new PdfSeparationColorSpace("MySpotColor", Color.DarkGreen);
            PdfSeparationColorSpace cs2 = new PdfSeparationColorSpace("MySpotColor", Color.Yellow);
            PdfSeparationColorSpace cs3 = new PdfSeparationColorSpace("MySpotColor", Color.DeepPink);
            PdfSeparationColor color1 = new PdfSeparationColor(cs1, 1f);
            PdfSeparationColor color2 = new PdfSeparationColor(cs2, 1f);
            PdfSeparationColor color3 = new PdfSeparationColor(cs3, 1f);

步骤3:根据颜色创建画刷

            PdfSolidBrush brush1 = new PdfSolidBrush(color1);
            PdfSolidBrush brush2 = new PdfSolidBrush(color2);
            PdfSolidBrush brush3 = new PdfSolidBrush(color3);

步骤4:绘入图形及文字,应用色彩透明度到图形

            //绘入图形及文字并着色
            page.Canvas.DrawPie(brush1, 10, 30, 60, 60, 360, 360);
            page.Canvas.DrawPie(brush2, 10, 120, 60, 60, 360, 360);
            page.Canvas.DrawPie(brush3, 10, 210, 60, 60, 360, 360);
            page.Canvas.DrawString("透明度=1.0", new PdfTrueTypeFont(new Font("Arial Unicode MS", 10f), true), brush1, new PointF(16, 100));

            //将基本色透明度设置为0.5,并绘入图片及文字
            color1 = new PdfSeparationColor(cs1, 0.5f);
            brush1 = new PdfSolidBrush(color1);
            page.Canvas.DrawPie(brush1, 80, 30, 60, 60, 360, 360);
            color2 = new PdfSeparationColor(cs2, 0.5f);
            brush2 = new PdfSolidBrush(color2);
            page.Canvas.DrawPie(brush2, 80, 120, 60, 60, 360, 360);
            color3 = new PdfSeparationColor(cs3, 0.5f);
            brush3 = new PdfSolidBrush(color3);
            page.Canvas.DrawPie(brush3, 80, 210, 60, 60, 360, 360);

            page.Canvas.DrawString("透明度=0.5", new PdfTrueTypeFont(new Font("Arial Unicode MS", 10f), true), brush1, new PointF(86, 100));

            //将基本色透明度设置为0.25,并绘入图片及文字
            color1 = new PdfSeparationColor(cs1, 0.25f);
            brush1 = new PdfSolidBrush(color1);
            page.Canvas.DrawPie(brush1, 150, 30, 60, 60, 360, 360);
            color2 = new PdfSeparationColor(cs2, 0.25f);
            brush2 = new PdfSolidBrush(color2);
            page.Canvas.DrawPie(brush2, 150, 120, 60, 60, 360, 360);
            color3 = new PdfSeparationColor(cs3, 0.25f);
            brush3 = new PdfSolidBrush(color3);
            page.Canvas.DrawPie(brush3, 150, 210, 60, 60, 360, 360);
            page.Canvas.DrawString("透明度=0.25", new PdfTrueTypeFont(new Font("Arial Unicode MS", 10f), true), brush1, new PointF(156, 100));

步骤5:保存文档

            doc.SaveToFile("设置透明度.pdf");
            System.Diagnostics.Process.Start("设置透明度.pdf");

色彩透明度实现效果:
C# 绘制PDF图形——基本图形、自定义图形、色彩透明度

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