转换 PDF 文件

将 PDF 页面转换为不同的图像格式 (Facades)

为了将 PDF 页面转换为不同的图像格式，您需要创建 PdfConverter 对象，并使用 BindPdf 方法打开 PDF 文件。之后，您需要调用 DoConvert 方法进行初始化任务。然后，您可以使用 HasNextImage 和 GetNextImage 方法循环遍历所有页面。GetNextImage 方法允许您创建特定页面的图像。您还需要将 ImageFormat 传递给此方法，以便创建特定类型的图像，即 JPEG、GIF 或 PNG 等。最后，调用 PdfConverter 类的 Close 方法。以下代码片段向您展示如何将 PDF 页面转换为图像。

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfPagesToImages01()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_Images();

    // Create PdfConverter object
    using (var converter = new Aspose.Pdf.Facades.PdfConverter())
    {
        // Bind PDF document
        converter.BindPdf(dataDir + "ConvertPdfPagesToImages.pdf");

        // Initialize the converting process
        converter.DoConvert();

        // Check if pages exist and then convert to image one by one
        while (converter.HasNextImage())
        {
            // Generate output file name with '_out' suffix
            var outputFileName = dataDir + System.DateTime.Now.Ticks.ToString() + "_out.jpg";
            // Convert the page to image and save it
            converter.GetNextImage(outputFileName, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}

在下一个代码片段中，我们将展示如何更改一些参数。通过 CoordinateType 我们设置框架为 ‘CropBox’。此外，我们可以通过指定每英寸的点数来更改 Resolution。下一个 FormPresentationMode - 表单呈现模式。然后我们指明 StartPage，设置转换开始的页面编号。我们还可以通过设置范围来指定最后一页。

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertPdfPagesToImages02()
{
    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf_Images();

    // Create PdfConverter object
    using (var converter = new Aspose.Pdf.Facades.PdfConverter())
    {
        // Bind PDF document
        converter.BindPdf(dataDir + "ConvertPdfPagesToImages.pdf");

        // Initialize the converting process
        converter.DoConvert();

        // Set additional conversion settings
        converter.CoordinateType = Aspose.Pdf.PageCoordinateType.CropBox;
        converter.Resolution = new Aspose.Pdf.Devices.Resolution(600);
        converter.FormPresentationMode = Aspose.Pdf.Devices.FormPresentationMode.Production;
        converter.StartPage = 2;

        // Check if pages exist and then convert to image one by one
        while (converter.HasNextImage())
        {
            // Generate output file name
            var outputFileName = dataDir + System.DateTime.Now.Ticks.ToString() + "_out.jpg";
            // Convert the page to image and save it
            converter.GetNextImage(outputFileName, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}

使用自定义字体替换将 PDF 页面转换为图像格式

在下一个代码片段中，我们演示如何在 PDF 到图像转换过程中应用自定义字体替换。我们使用 FontRepository.Substitutions 集合来注册自定义替换规则。在此示例中，当遇到字体 “Helvetica” 时，它将被替换为 “Arial”。

.NET Core 3.1

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertWithCustomFontSubstitution()
{
    // Add custom font substitution
    Aspose.Pdf.Text.FontRepository.Substitutions.Add(new CustomPdfFontSubstitution());

    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf();
    
    using (var converter = new Aspose.Pdf.Facades.PdfConverter())
    {
        // Bind PDF document
        converter.BindPdf(dataDir + "ConvertWithSubstitution.pdf");

        // Initialize the converting process
        converter.DoConvert();

        // Check if pages exist and then convert to image one by one
        while (converter.HasNextImage())
        {
            // Generate output file name with '_out' suffix
            var outputFileName = dataDir + System.DateTime.Now.Ticks.ToString() + "_out.jpg";
            // Convert the page to image and save it
            converter.GetNextImage(outputFileName, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
    }
}

private class CustomPdfFontSubstitution : Aspose.Pdf.Text.CustomFontSubstitutionBase
{
    public override bool TrySubstitute(
        Aspose.Pdf.Text.CustomFontSubstitutionBase.OriginalFontSpecification originalFontSpecification,
        out Aspose.Pdf.Text.Font substitutionFont)
    {
        if (originalFontSpecification.OriginalFontName == "Helvetica")
        {
            substitutionFont = Aspose.Pdf.Text.FontRepository.FindFont("Arial");
            return true;
        }
        // Default substitution logic
        return base.TrySubstitute(originalFontSpecification, out substitutionFont);
    }
}

.NET 8

// For complete examples and data files, visit https://github.com/aspose-pdf/Aspose.PDF-for-.NET
private static void ConvertWithCustomFontSubstitution()
{
    // Add custom font substitution
    Aspose.Pdf.Text.FontRepository.Substitutions.Add(new CustomPdfFontSubstitution());

    // The path to the documents directory
    var dataDir = RunExamples.GetDataDir_AsposePdf();
    
    using var converter = new Aspose.Pdf.Facades.PdfConverter();
    
    // Bind PDF document
    converter.BindPdf(dataDir + "ConvertWithSubstitution.pdf");

    // Initialize the converting process
    converter.DoConvert();

    // Check if pages exist and then convert to image one by one
    while (converter.HasNextImage())
    {
        // Generate output file name with '_out' suffix
        var outputFileName = dataDir + System.DateTime.Now.Ticks.ToString() + "_out.jpg";
        // Convert the page to image and save it
        converter.GetNextImage(outputFileName, System.Drawing.Imaging.ImageFormat.Jpeg);
    }
}

private class CustomPdfFontSubstitution : Aspose.Pdf.Text.CustomFontSubstitutionBase
{
    public override bool TrySubstitute(
        Aspose.Pdf.Text.CustomFontSubstitutionBase.OriginalFontSpecification originalFontSpecification,
        out Aspose.Pdf.Text.Font substitutionFont)
    {
        if (originalFontSpecification.OriginalFontName == "Helvetica")
        {
            substitutionFont = Aspose.Pdf.Text.FontRepository.FindFont("Arial");
            return true;
        }
        // Default substitution logic
        return base.TrySubstitute(originalFontSpecification, out substitutionFont);
    }
}

另请参见

Aspose.PDF for .NET 允许将 PDF 文档转换为各种格式，也可以从其他格式转换为 PDF。此外，您可以检查 Aspose.PDF 转换的质量，并使用 Aspose.PDF 转换器应用程序在线查看结果。了解 转换 部分以解决您的任务。