无法在具有图像的 iTextSharp 文档中添加边距

Question

要求： 大图像（动态）需要拆分并显示在 PDF 页面中。如果图像不能容纳在一个页面中，那么我们需要添加另一个页面并尝试适应剩余部分等等。

到目前为止，我可以将图像拆分为多个页面，但是它们似乎完全忽略了边距值，因此显示的图像没有任何边距。

请看下面的代码：

string fileStringReplace = imageByteArray.Replace("data:image/jpeg;base64,", "");
        Byte[] imageByte = Convert.FromBase64String(fileStringReplace);
        iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(imageByte);
        float w = image.ScaledWidth;
        float h = image.ScaledHeight;
        float cropHeight = 1500f;

        iTextSharp.text.Rectangle page = new iTextSharp.text.Rectangle(1150f, cropHeight);
        var x = page.Height;
        Byte[] created;

        iTextSharp.text.Document document = new iTextSharp.text.Document(page, 20f, 20f, 20f, 40f); --This has no impact

        using (var outputMemoryStream = new MemoryStream())
        {
            PdfWriter writer = PdfWriter.GetInstance(document, outputMemoryStream);
            writer.CloseStream = false;

            document.Open();
            PdfContentByte canvas = writer.DirectContentUnder;

            float usedHeights = h;

            while (usedHeights >= 0)
            {
                usedHeights -= cropHeight;
                document.SetPageSize(new iTextSharp.text.Rectangle(1150f, cropHeight));
                canvas.AddImage(image, w, 0, 0, h, 0, -usedHeights);

                document.NewPage();
            }

            document.Close();

            created = outputMemoryStream.ToArray();

            outputMemoryStream.Write(created, 0, created.Length);
            outputMemoryStream.Position = 0;
        }
        return created;

我还尝试通过 document.SetMargins() 在循环中设置边距 - 但这不起作用。

Answer 1

你正在混合不同的东西。

当您创建边距时，无论是在构造 Document 实例时还是使用 setMargins() 方法时，您都会为让 iText(Sharp) 决定布局时创建边距。也就是说：当您执行document.Add(image) 之类的操作时，将尊重边距。

但是，您不允许 iText 创建布局。您创建了一个名为 canvas 的 PdfContentByte，并决定使用转换矩阵将图像添加到该画布。这意味着您将计算 AddImage() 方法所需的 a、b、c、d、e 和 f 值。

你应该做那个数学。如果你想看到一个边距，那么值 w、0、0、h、0 和 -usedHeights 是错误的，你不应该责怪 iTextSharp，你应该责怪你的对解析几何缺乏洞察力（这是你 16 岁在高中时学到的东西）。

这对你来说可能更容易：

iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(imageByte);
float w = image.ScaledWidth;
float h = image.ScaledHeight;
// For the sake of simplicity, I don't crop the image, I just add 20 user units
iTextSharp.text.Rectangle page = new iTextSharp.text.Rectangle(w + 20, h + 20);
iTextSharp.text.Document document = new iTextSharp.text.Document(page);
PdfWriter writer = PdfWriter.GetInstance(document, outputMemoryStream);
// Please drop the line that prevents closing the output stream!
// Why are so many people making this mistake?
// Who told you you shouldn't close the output stream???
document.Open();
// We define an absolute position for the image
// it will leave a margin of 10 to the left and to the bottom
// as we created a page that is 20 user units to wide and to high,
// we will also have a margin of 10 to the right and to the top
img.SetAbsolutePosition(10, 10);
document.Add(Image);
document.Close();

请注意，SetAbsolutePosition() 还可以让您控制，而不管边距如何，作为替代方案，您可以使用：

iTextSharp.text.Image image = iTextSharp.text.Image.GetInstance(imageByte);
float w = image.ScaledWidth;
float h = image.ScaledHeight;
// For the sake of simplicity, I don't crop the image, I just add 20 user units
iTextSharp.text.Rectangle page = new iTextSharp.text.Rectangle(w + 20, h + 20);
iTextSharp.text.Document document = new iTextSharp.text.Document(page, 10, 10, 10, 10);
PdfWriter writer = PdfWriter.GetInstance(document, outputMemoryStream);
// Please drop the line that prevents closing the output stream!
// Why are so many people making this mistake?
// Who told you you shouldn't close the output stream???
document.Open();
// We add the image to the document, and we let iTextSharp decide where to put it
// As there is just sufficient space to fit the image inside the page, it should fit,
// But be aware of the existence of a leading; that could create side-effects
// such as forwarding the image to the next page because it doesn't fit vertically
document.Add(Image);
document.Close();