使用iTextSharp自动缩放图像 [英] Auto scaling of Images with iTextSharp

问题描述

我正在使用iTextSharp API从C#4.0 Windows应用程序生成PDF文件.我将传递HTML字符串，其中将包含RTF和图片.我的PDF文件大小为A4，带有默认边距.请注意，当我的图片尺寸较大(例如，height ="701px" width ="935px")时，该图片将无法转换为PDF.看起来，我必须按比例缩小图像尺寸，以适合PDF A4尺寸.我通过将图片粘贴到A4大小的Word文档中进行了检查，MS Word自动将图片缩小36％，即MS Word仅占用原始图片尺寸的64％，并设置了绝对高度&宽度.

I’m generating PDF files from my C# 4.0 windows application using iTextSharp API. I’ll be passing HTML string which will contain Rich Text and Images. My PDF file size is A4 with default margins. Noticed that when I have a large image in dimension (e.g. height="701px" width="935px") , the image is not coming to PDF. Looks like, I have to scale down the image dimension which should be able to fit in the PDF A4 size. I checked this by pasting the image to a word document of A4 size, MS Word automatically scales down the image by 36% i.e. MS Word takes only 64% of the original image dimension and sets the absolute height & width.

有人可以帮助模仿C#中的类似行为吗?

Can someone please help to mimic similar behavior in C#?

让我知道如何自动设置图像高度和宽度以适合A4 PDF文件.

Let me know how to automatically set an image height & width to fit in A4 PDF file.

推荐答案

是的，iTextSharp 不会自动调整对于文档太大的图像的大小.因此，这只是一个问题:

That's correct, iTextSharp won't automatically size images that are too big for the document. So it's just a matter of:

• 使用左/右和上/下页边距计算可用文档的宽度和高度.
• 获取图像的宽度和高度.
• 将文档的宽度和高度与图像的宽度和高度进行比较.
• 根据需要缩放图像.

这是一种方法，请参见内联注释:

Here's one way, see inline comments:

// change this to any page size you want    
Rectangle defaultPageSize = PageSize.A4;   
using (Document document = new Document(defaultPageSize)) {
  PdfWriter.GetInstance(document, STREAM);
  document.Open();
// if you don't account for the left/right margins, the image will
// run off the current page
  float width = defaultPageSize.Width
    - document.RightMargin
    - document.LeftMargin
  ;
  float height = defaultPageSize.Height
    - document.TopMargin
    - document.BottomMargin
  ;
  foreach (string path in imagePaths) {
    Image image = Image.GetInstance(path);
    float h = image.ScaledHeight;
    float w = image.ScaledWidth;
    float scalePercent;
// scale percentage is dependent on whether the image is 
// 'portrait' or 'landscape'        
    if (h > w) {
// only scale image if it's height is __greater__ than
// the document's height, accounting for margins
      if (h > height) {
        scalePercent = height / h;
        image.ScaleAbsolute(w * scalePercent, h * scalePercent);
      }
    }
    else {
// same for image width        
      if (w > width) {
        scalePercent = width / w;
        image.ScaleAbsolute(w * scalePercent, h * scalePercent);
      }
    }
    document.Add(image);
  }
}

唯一值得注意的一点是，上面的imagePaths是string[]，因此您可以测试在添加大到适合页面大小的图像集合时发生的情况.

The only point worth noting is that imagePaths above is a string[] so that you can test what happens when adding a collection of images that are to big to fit in a page.

另一种方法是将图像放在一个列中，单个单元格

Another way is to put the image in a one column, single cell PdfPTable:

PdfPTable table = new PdfPTable(1);
table.WidthPercentage = 100;
foreach (string path in imagePaths) {
  Image image = Image.GetInstance(path);
  PdfPCell cell = new PdfPCell(image, true);
  cell.Border = Rectangle.NO_BORDER;
  table.AddCell(cell);
}
document.Add(table);

这篇关于使用iTextSharp自动缩放图像的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！