// 完毕:
using System;
using System.IO;
using System.Drawing;
using System.Collections.Generic;
using GrapeCity.Documents.Pdf;
using GrapeCity.Documents.Pdf.Graphics.Images;
using GrapeCity.Documents.Pdf.Spec;
using GrapeCity.Documents.Text;
using GrapeCity.Documents.Drawing;
namespace DsPdfWeb.Demos
{
// This example shows how to fetch low level information about images living in a PDF file,
// such as the ID of the image object in the PDF, the filter used to store the image,
// the decoder parameters, the content of the PdfImage dictionary, etc.
// The original PDF is appended to the result for reference.
public class GetImageProperties
{
public int CreatePDF(Stream stream)
{
using var fs = File.OpenRead(Path.Combine("Resources", "PDFs", "Wetlands.pdf"));
var docSrc = new GcPdfDocument();
docSrc.Load(fs);
// Get the images in the loaded PDF and print their info into the resulting PDF:
var imageInfos = docSrc.GetImages();
// The PDF to hold the results:
var doc = new GcPdfDocument();
var page = doc.NewPage();
// Set up a TextLayout to format the results:
var tl = page.Graphics.CreateTextLayout();
tl.DefaultFormat.Font = StandardFonts.Courier;
tl.DefaultFormat.FontSize = 14;
tl.MaxWidth = doc.PageSize.Width;
tl.MaxHeight = doc.PageSize.Height;
tl.MarginAll = tl.Resolution;
var captionFmt = new TextFormat(tl.DefaultFormat) { Font = StandardFonts.CourierBold, FontSize = tl.DefaultFormat.FontSize + 2 };
int i = 0;
foreach (var imageInfo in imageInfos)
{
tl.AppendLine($"Image {++i}", captionFmt);
// PdfImageBase class represents an image in the loaded PDF file:
PdfImageBase img = imageInfo.Image;
tl.AppendLine($"PdfImage object ID: {img.ObjID}");
// PdfImageBase is derived from PdfDictWrapper type, it has methods
// that allow you to access properties/data of the underlying PDF stream object:
using (PdfStreamInfo psi = img.GetPdfStreamInfo())
{
tl.AppendLine($" Image stream length: {psi.Stream.Length}");
tl.AppendLine($" ImageFilterName: {psi.ImageFilterName}");
tl.AppendLine($"ImageFilterDecodeParams: {psi.ImageFilterDecodeParams}");
// Dump the content of the ImageFilterDecodeParams if it exists:
if (psi.ImageFilterDecodeParams != null)
{
foreach (var kvp in psi.ImageFilterDecodeParams.Dict)
{
tl.AppendLine($"{kvp.Key}: {kvp.Value}");
}
// An example of how to get the value of BlackIs1:
var blackIs1 = psi.ImageFilterDecodeParams.GetBool(PdfName.Std.BlackIs1, null);
tl.AppendLine($"BlackIs1: {blackIs1}");
}
}
// Dump the properties of PdfImage dictionary:
tl.AppendLine();
tl.AppendLine("Properties of PdfImage dictionary:");
foreach (KeyValuePair<PdfName, IPdfObject> kvp in img.PdfDict.Dict)
{
tl.AppendLine($"{kvp.Key}: {kvp.Value}");
}
//
var cs = img.Get<IPdfObject>(PdfName.Std.ColorSpace);
tl.AppendLine($"ColorSpace: {cs.GetType().Name} {cs}");
var bpc = img.Get<IPdfObject>(PdfName.Std.BitsPerComponent);
tl.AppendLine($"BitsPerComponent: {bpc?.GetType().Name} {bpc}");
tl.AppendLine();
}
// Render the results:
tl.PerformLayout(true);
while (true)
{
var splitResult = tl.Split(null, out TextLayout rest);
page.Graphics.DrawTextLayout(tl, PointF.Empty);
if (splitResult != SplitResult.Split)
break;
tl = rest;
tl.MarginTop = tl.Resolution;
page = doc.Pages.Add();
}
// Append the source PDF to the result for reference:
doc.MergeWithDocument(docSrc);
// 完毕:
doc.Save(stream);
return doc.Pages.Count;
}
}
}