Aspose.Pdf for .NET是一款专门用于处理PDF文档的控件，不仅可以创建、编辑和保存PDF文档，还可以对PDF文档进行各种复杂的操作、分割、合并、插入页眉页脚、添加水印、转换为其它文档格式等，在新发布了12.0后开发人员可以利用API对PDF文档内的图形对象进行渐变色的填充，具体可以参考下面的C#代码：

// Create Document instance

Document doc = new Document();

// Add page to pages collection of PDF file

Aspose.Pdf.Page page = doc.Pages.Add();

// Create Graph instance

Aspose.Pdf.Drawing.Graph graph = new Aspose.Pdf.Drawing.Graph(300, 300);

// Add graph object to paragraphs collection of page instance

page.Paragraphs.Add(graph);

// Create Rectangle instance

Aspose.Pdf.Drawing.Rectangle rect = new Aspose.Pdf.Drawing.Rectangle(0, 0, 300, 300);

// Add rectangle object to shapes collection of Graph object

graph.Shapes.Add(rect);

// Specify Gradient fill color for Graph object

rect.GraphInfo.FillColor = new Aspose.Pdf.Color

{

PatternColorSpace = new Aspose.Pdf.Drawing.GradientAxialShading(Aspose.Pdf.Color.Red, Aspose.Pdf.Color.Blue) { Start = new Aspose.Pdf.Point(0, 0), End = new Aspose.Pdf.Point(300, 300) }

};

// Save PDF file

doc.Save("GradiantFill.PDF");