////////////////////////////////////////////////////////////////////
// Parse inline image
////////////////////////////////////////////////////////////////////
internal PdfOp ParseInlineImage()
{
// create empty dictionary
PdfDictionary ImageDict = ParseDictionary(true);
// get image width
if (!ImageDict.FindValue("/W").GetInteger(out int Width) || Width <= 0)
{
throw new ApplicationException("Parse inline image: Width error");
}
// get image height
if (!ImageDict.FindValue("/H").GetInteger(out int Height) || Height <= 0)
{
throw new ApplicationException("Parse inline image: Height error");
}
// get image bits per component
if (!ImageDict.FindValue("/BPC").GetInteger(out int BitPerComp) ||
BitPerComp != 1 && BitPerComp != 2 && BitPerComp != 4 && BitPerComp != 8)
{
throw new ApplicationException("Parse inline image: BPC error");
}
int Components = 0;
// get color space
string ColorSpace = ImageDict.FindValue("/CS").ToName;
if (ColorSpace != null)
{
// number of components
if (ColorSpace == "/G")
{
Components = 1;
}
else if (ColorSpace == "/RGB")
{
Components = 3;
}
else if (ColorSpace == "/CMYK")
{
Components = 4;
}
else
{
throw new ApplicationException("Parse inline image: ColorSpace error");
}
}
ImageDict.FindValue("/IM").GetBoolean(out bool IM);
if (IM)
{
Components = 1;
}
PdfBase Filter = ImageDict.FindValue("/F");
if (!Filter.IsEmpty)
{
throw new ApplicationException("Parse inline image: No filter support");
}
// no ASCIIHexDecode AHx or ASCII85Decode A85
if (!PdfBase.IsWhiteSpace(NextChar))
{
throw new ApplicationException("Parse inline image: ID must be followed by white space");
}
// image width in bytes
int WidthBytes = 0;
switch (BitPerComp)
{
case 1:
WidthBytes = (Width + 7) / 8;
break;
case 2:
WidthBytes = (Width + 3) / 4;
break;
case 4:
WidthBytes = (Width + 1) / 2;
break;
case 8:
WidthBytes = Width;
break;
}
// image size
int Size = WidthBytes * Height * Components;
// image stream
byte[] ImageStream = new byte[Size];
for (int Index = 0; Index < Size; Index++)
{
// read next character
NextChar = ReadChar();
// end of file error
if (NextChar == EOF)
{
throw new ApplicationException("Invalid inline image (end of contents)");
}
// save it in bitmap
ImageStream[Index] = (byte)NextChar;
}
// get termination
NextChar = ReadChar();
SkipWhiteSpace();
if (NextChar != 'E' || ReadChar() != 'I')
{
throw new ApplicationException("Parse inline image: EI is missing");
}
NextChar = ReadChar();
PdfOp InlineImage = new PdfOp(Operator.BeginInlineImage);
InlineImage.ArgumentArray = new PdfBase[] { ImageDict, new PdfString(ImageStream) };
// exit
return(InlineImage);
}
/// <summary>
/// Apply predictor decode
/// </summary>
/// <param name="InputBuffer">Input buffer</param>
/// <returns>Output buffer</returns>
internal byte[] PredictorDecode
(
byte[] InputBuffer
)
{
// test for /DecodeParams
PdfDictionary DecodeParms = Dictionary.FindValue("/DecodeParms").ToDictionary;
// none found
if (DecodeParms == null)
{
return(InputBuffer);
}
// look for predictor code. if default (none or 1) do nothing
if (!DecodeParms.FindValue("/Predictor").GetInteger(out int Predictor) || Predictor == 1)
{
return(InputBuffer);
}
// we only support predictor code 12
if (Predictor != 12)
{
return(null);
}
// get width
DecodeParms.FindValue("/Columns").GetInteger(out int Width);
if (Width < 0)
{
throw new ApplicationException("/DecodeParms /Columns is negative");
}
if (Width == 0)
{
Width = 1;
}
// calculate rows
int Rows = InputBuffer.Length / (Width + 1);
if (Rows < 1)
{
throw new ApplicationException("/DecodeParms /Columns is greater than stream length");
}
// create output buffer
byte[] OutputBuffer = new byte[Rows * Width];
// reset pointers
int InPtr = 1;
int OutPtr = 0;
int OutPrevPtr = 0;
// first row (ignore filter)
while (OutPtr < Width)
{
OutputBuffer[OutPtr++] = InputBuffer[InPtr++];
}
// decode loop
for (int Row = 1; Row < Rows; Row++)
{
// first byte is filter
int Filter = InputBuffer[InPtr++];
// we support PNG filter up only
if (Filter != 2)
{
throw new ApplicationException("/DecodeParms Only supported filter is 2");
}
// convert input to output
for (int Index = 0; Index < Width; Index++)
{
OutputBuffer[OutPtr++] = (byte)(OutputBuffer[OutPrevPtr++] + InputBuffer[InPtr++]);
}
}
return(OutputBuffer);
}
