private static Bitmap PdfImageToBitmap(PdfDictionary image)
{
string filter = image.Elements.GetName(PdfDictionary.PdfStream.Keys.Filter);
switch (filter)
{
case "/DCTDecode":
byte[] stream = image.Stream.Value;
return(new Bitmap(new MemoryStream(stream)));
//Thanks to VacentViscera - https://forum.pdfsharp.net/viewtopic.php?f=8&t=3801
case "/FlateDecode":
int width = image.Elements.GetInteger(PdfImage.Keys.Width);
int height = image.Elements.GetInteger(PdfImage.Keys.Height);
int bitsPerComponent = image.Elements.GetInteger(PdfImage.Keys.BitsPerComponent);
FlateDecode flate = new FlateDecode();
byte[] imageData = flate.Decode(image.Stream.Value);
PixelFormat pixelFormat;
switch (bitsPerComponent)
{
case 1:
pixelFormat = PixelFormat.Format1bppIndexed;
break;
case 8:
pixelFormat = PixelFormat.Format8bppIndexed;
break;
case 24:
pixelFormat = PixelFormat.Format24bppRgb;
break;
default:
throw new Exception("Unknown pixel format: " + bitsPerComponent);
}
Bitmap bitmap = new Bitmap(width, height, pixelFormat);
var bmpData = bitmap.LockBits(new Rectangle(0, 0, width, height), ImageLockMode.WriteOnly, pixelFormat);
int length = (int)Math.Ceiling(width * bitsPerComponent / 8.0);
for (int i = 0; i < height; i++)
{
Marshal.Copy(imageData, i * length, new IntPtr(bmpData.Scan0.ToInt32() + i * bmpData.Stride), length);
}
bitmap.UnlockBits(bmpData);
return(bitmap);
default:
return(null);
}
}
private static PdfDictionary ProcessFilters(PdfDictionary dictionary)
{
PdfDictionary result;
// Create a dictionary mapping (i.e. switch statement) to process the expected filters.
var map = new Dictionary <string, Func <byte[], byte[]> >()
{
{ "/FlateDecode", (d) => {
var decoder = new FlateDecode();
return(decoder.Decode(d));
} }
};
// Get all of the filters.
var filters = ((PdfArray)dictionary.Elements["/Filter"])
.Elements.Where(e => e.IsName())
.Select(e => ((PdfName)e).Value)
.ToList();
// If only one filter in array. Just rewrite the /Filter
if (filters.Count == 1)
{
result = dictionary.Clone();
result.Elements["/Filter"] = new PdfName(filters[0]);
return(result);
}
// Process each filter in order. The last filter should be the actual encoded image.
byte[] data = dictionary.Stream.Value;
for (int index = 0; index < (filters.Count - 1); index++)
{
if (!map.ContainsKey(filters[index]))
{
throw new NotSupportedException(String.Format("Encountered embedded image with multiple filters: \"{0}\". Unable to process the filter: \"{1}\".",
String.Join(",", filters), filters[index]));
}
data = map[filters[index]].Invoke(data);
}
result = new PdfDictionary();
result.Elements.Add("/Filter", new PdfName(filters.Last()));
foreach (var element in dictionary.Elements.Where(e => !String.Equals(e.Key, "/Filter", StringComparison.OrdinalIgnoreCase)))
{
result.Elements.Add(element.Key, element.Value);
}
result.CreateStream(data);
return(result);
}
