Why is my image distorted when decoding as FlateDecode using iTextSharp?

Question

When decoding an image within a PDF as FlateDecode via iTextSharp the image is distorted and I can\'t seem to figure out why.

The recognized bpp is

Answer 1

Try copy your data row by row, maybe it will solve the problem.

int w = imgObj.GetAsNumber(PdfName.WIDTH).IntValue;
int h = imgObj.GetAsNumber(PdfName.HEIGHT).IntValue;
int bpp = imgObj.GetAsNumber(PdfName.BITSPERCOMPONENT).IntValue;
var pixelFormat = PixelFormat.Format1bppIndexed;

byte[] rawBytes = PdfReader.GetStreamBytesRaw((PRStream)imgObj);
byte[] decodedBytes = PdfReader.FlateDecode(rawBytes);
byte[] streamBytes = PdfReader.DecodePredictor(decodedBytes, imgObj.GetAsDict(PdfName.DECODEPARMS));
// byte[] streamBytes = PdfReader.GetStreamBytes((PRStream)imgObj); // same result as above 3 lines of code.

using (Bitmap bmp = new Bitmap(w, h, pixelFormat))
{
    var bmpData = bmp.LockBits(new Rectangle(0, 0, w, h), ImageLockMode.WriteOnly, pixelFormat);
    int length = (int)Math.Ceiling(w * bpp / 8.0);
    for (int i = 0; i < h; i++)
    {
        int offset = i * length;
        int scanOffset = i * bmpData.Stride;
        Marshal.Copy(streamBytes, offset, new IntPtr(bmpData.Scan0.ToInt32() + scanOffset), length);
    }
    bmp.UnlockBits(bmpData);

    bmp.Save(fileName);
}