Itextsharp锐化渐变背景
Itextsharp锐化渐变背景
提问于 2011-10-07 14:58:33
有没有办法将渐变背景设置为pdfcell或段落？或者我必须使用image？
回答 2
Stack Overflow用户
回答已采纳
发布于 2011-10-07 22:51:56
可以，iText和iTextSharp支持渐变颜色。PdfShading对象有几个静态方法，可以为您创建不同类型的PdfShading对象。您最感兴趣的两个可能是SimpleAxial和SimpleRadial。还有另外三个名字是Type1，Type2和Type3，我还没有探索过。
一旦有了PdfShading对象，就可以直接从它创建一个PdfShadingPattern，一旦有了，就可以从它创建一个ShadingColor。ShadingColor最终是从BaseColor派生而来的，所以您应该能够在使用它的任何地方使用它。在您的示例中，您希望将其分配给一个BackgroundColor。
下面是一个针对iTextSharp 5.1.1.0的完整的工作WinForms应用程序，其中显示了创建了一个包含两列的表，每一列都有自己的渐变背景色。
注意：PdfShading静态方法的(x，y)坐标是文档级的，而不是单元格级的。这意味着，根据渐变的大小，您可能无法重用PdfShading对象。在下面的示例之后，我将向您展示如何使用单元格事件克服此限制。
using System;
using System.Text;
using System.Windows.Forms;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
//Test file name
string TestFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Test.pdf");
//Standard iTextSharp setup
using (FileStream fs = new FileStream(TestFile, FileMode.Create, FileAccess.Write, FileShare.None))
{
using (Document doc = new Document(PageSize.LETTER))
{
using (PdfWriter w = PdfWriter.GetInstance(doc, fs))
{
//Open the document for writing
doc.Open();
//Create a shading object. The (x,y)'s appear to be document-level instead of cell-level so they need to be played with
PdfShading shading = PdfShading.SimpleAxial(w, 0, 700, 300, 700, BaseColor.BLUE, BaseColor.RED);
//Create a pattern from our shading object
PdfShadingPattern pattern = new PdfShadingPattern(shading);
//Create a color from our patter
ShadingColor color = new ShadingColor(pattern);
//Create a standard two column table
PdfPTable t = new PdfPTable(2);
//Add a text cell setting the background color through object initialization
t.AddCell(new PdfPCell(new Phrase("Hello")) { BackgroundColor = color });
//Add another cell with everything inline. Notice that the (x,y)'s have been updated
t.AddCell(new PdfPCell(new Phrase("World")) { BackgroundColor = new ShadingColor(new PdfShadingPattern(PdfShading.SimpleAxial(w, 400, 700, 600, 700, BaseColor.PINK, BaseColor.CYAN))) });
//Add the table to the document
doc.Add(t);
//Close the document
doc.Close();
}
}
}
this.Close();
}
}
}示例2
如上所述，上面的方法使用文档级位置，这通常不够好。要克服这个问题，您需要使用单元格级定位，并且需要使用单元格事件，因为单元格位置在表本身呈现之前是不知道的。要使用单元格事件，您需要创建一个实现IPdfPCellEvent并处理CellLayout方法的新类。下面是完成这一切的更新代码：
using System;
using System.Text;
using System.Windows.Forms;
using iTextSharp.text;
using iTextSharp.text.pdf;
using System.IO;
namespace WindowsFormsApplication1
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
//Test file name
string TestFile = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.Desktop), "Test.pdf");
//Standard iTextSharp setup
using (FileStream fs = new FileStream(TestFile, FileMode.Create, FileAccess.Write, FileShare.None))
{
using (Document doc = new Document(PageSize.LETTER))
{
using (PdfWriter w = PdfWriter.GetInstance(doc, fs))
{
//Open the document for writing
doc.Open();
//Create a standard two column table
PdfPTable t = new PdfPTable(2);
//Create an instance of our custom cell event class, passing in our main writer which is needed by the PdfShading object
var CE = new GradientBackgroundEvent(w);
//Set the default cell's event to our handler
t.DefaultCell.CellEvent = CE;
//Add cells normally
t.AddCell("Hello");
t.AddCell("World");
//Add the table to the document
doc.Add(t);
//Close the document
doc.Close();
}
}
}
this.Close();
}
public class GradientBackgroundEvent : IPdfPCellEvent
{
//Holds pointer to main PdfWriter object
private PdfWriter w;
//Constructor
public GradientBackgroundEvent(PdfWriter w)
{
this.w = w;
}
public void CellLayout(PdfPCell cell, Rectangle position, PdfContentByte[] canvases)
{
//Create a shading object with cell-specific coords
PdfShading shading = PdfShading.SimpleAxial(w, position.Left, position.Bottom, position.Right, position.Top, BaseColor.BLUE, BaseColor.RED);
//Create a pattern from our shading object
PdfShadingPattern pattern = new PdfShadingPattern(shading);
//Create a color from our patter
ShadingColor color = new ShadingColor(pattern);
//Get the background canvas. NOTE, If using an older version of iTextSharp (4.x) you might need to get the canvas in a different way
PdfContentByte cb = canvases[PdfPTable.BACKGROUNDCANVAS];
//Set the background color of the given rectable to our shading pattern
position.BackgroundColor = color;
//Fill the rectangle
cb.Rectangle(position);
}
}
}
}Stack Overflow用户
发布于 2012-02-09 18:42:21
如果其他人还感兴趣，我想知道如何用渐变来给整个背景上色，你可以这样做……
PdfShading shading = PdfShading.simpleAxial(writer, 0, pageH, pageW, 0,
BaseColor.WHITE, BaseColor.LIGHT_GRAY);
PdfShadingPattern pattern = new PdfShadingPattern(shading);
cb.setShadingFill(pattern);
// cb.circle(500, 500, 500);
cb.rectangle(0, 0, pageW, pageH);
cb.fill();页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/7684002
复制相关文章
相似问题
腾讯云开发者
