/// <summary>
/// Reads chunkd from input stream, adds to ChunksList, and returns it.
/// If it's skipped, a PngChunkSkipped object is created
/// </summary>
PngChunk ReadChunk(byte[] chunkid, int clen, bool skipforced)
{
if (clen < 0)
{
throw new IO.IOException($"invalid chunk lenght: {clen}");
}
// skipChunksByIdSet is created lazyly, if fist IHDR has already been read
if (skipChunkIdsSet == null && CurrentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR)
{
skipChunkIdsSet = new Dictionary <string, int>();
if (SkipChunkIds != null)
{
foreach (string id in SkipChunkIds)
{
skipChunkIdsSet.Add(id, 1);
}
}
}
string chunkidstr = ChunkHelper.ToString(chunkid);
PngChunk pngChunk = null;
bool critical = ChunkHelper.IsCritical(chunkidstr);
bool skip = skipforced;
if (MaxTotalBytesRead > 0 && clen + offset > MaxTotalBytesRead)
{
throw new IO.IOException($"Maximum total bytes to read exceeeded: {MaxTotalBytesRead} offset:{offset} clen={clen}");
}
// an ancillary chunks can be skipped because of several reasons:
if (CurrentChunkGroup > ChunksList.CHUNK_GROUP_0_IDHR && !ChunkHelper.IsCritical(chunkidstr))
{
skip = skip ||
(SkipChunkMaxSize > 0 && clen >= SkipChunkMaxSize) ||
skipChunkIdsSet.ContainsKey(chunkidstr) ||
(MaxBytesMetadata > 0 && clen > MaxBytesMetadata - bytesChunksLoaded) ||
!ChunkHelper.ShouldLoad(chunkidstr, ChunkLoadBehaviour);
}
if (skip)
{
PngHelperInternal.SkipBytes(inputStream, clen);
PngHelperInternal.ReadInt4(inputStream); // skip - we dont call PngHelperInternal.skipBytes(inputStream, clen + 4) for risk of overflow
pngChunk = new PngChunkSkipped(chunkidstr, ImgInfo, clen);
}
else
{
ChunkRaw chunk = new ChunkRaw(clen, chunkid, true);
chunk.ReadChunkData(inputStream, crcEnabled || critical);
pngChunk = PngChunk.Factory(chunk, ImgInfo);
if (!pngChunk.Crit)
{
bytesChunksLoaded += chunk.Len;
}
}
pngChunk.Offset = offset - 8L;
chunksList.AppendReadChunk(pngChunk, CurrentChunkGroup);
offset += clen + 4L;
return(pngChunk);
}
/// <summary>
/// Reads chunks before first IDAT. Position before: after IDHR (crc included)
/// Position after: just after the first IDAT chunk id Returns length of first
/// IDAT chunk , -1 if not found
/// </summary>
///
void ReadFirstChunks()
{
if (!FirstChunksNotYetRead())
{
return;
}
int clen = 0;
bool found = false;
byte[] chunkid = new byte[4]; // it's important to reallocate in each
this.CurrentChunkGroup = ChunksList.CHUNK_GROUP_1_AFTERIDHR;
while (!found)
{
clen = PngHelperInternal.ReadInt4(inputStream);
offset += 4;
if (clen < 0)
{
break;
}
PngHelperInternal.ReadBytes(inputStream, chunkid, 0, 4);
offset += 4;
if (PngCsUtils.arraysEqual4(chunkid, Pngcs.Chunks.ChunkHelper.b_IDAT))
{
found = true;
this.CurrentChunkGroup = ChunksList.CHUNK_GROUP_4_IDAT;
// add dummy idat chunk to list
chunksList.AppendReadChunk(new PngChunkIDAT(ImgInfo, clen, offset - 8), CurrentChunkGroup);
break;
}
else if (PngCsUtils.arraysEqual4(chunkid, Pngcs.Chunks.ChunkHelper.b_IEND))
{
throw new PngjInputException("END chunk found before image data (IDAT) at offset=" + offset);
}
string chunkids = ChunkHelper.ToString(chunkid);
if (chunkids.Equals(ChunkHelper.PLTE))
{
this.CurrentChunkGroup = ChunksList.CHUNK_GROUP_2_PLTE;
}
ReadChunk(chunkid, clen, false);
if (chunkids.Equals(ChunkHelper.PLTE))
{
this.CurrentChunkGroup = ChunksList.CHUNK_GROUP_3_AFTERPLTE;
}
}
int idatLen = found ? clen : -1;
if (idatLen < 0)
{
throw new PngjInputException("first idat chunk not found!");
}
iIdatCstream = new PngIDatChunkInputStream(inputStream, idatLen, offset);
idatIstream = ZlibStreamFactory.createZlibInputStream(iIdatCstream, true);
if (!crcEnabled)
{
iIdatCstream.DisableCrcCheck();
}
}
/// <summary>
/// Reads (and processes ... up to a point) chunks after last IDAT.
/// </summary>
///
void ReadLastChunks()
{
CurrentChunkGroup = ChunksList.CHUNK_GROUP_5_AFTERIDAT;
// PngHelper.logdebug("idat ended? " + iIdatCstream.isEnded());
if (!iIdatCstream.IsEnded())
{
iIdatCstream.ForceChunkEnd();
}
int clen = iIdatCstream.GetLenLastChunk();
byte[] chunkid = iIdatCstream.GetIdLastChunk();
bool endfound = false;
bool first = true;
bool skip = false;
while (!endfound)
{
skip = false;
if (!first)
{
clen = PngHelperInternal.ReadInt4(inputStream);
offset += 4;
if (clen < 0)
{
throw new PngjInputException("bad len " + clen);
}
PngHelperInternal.ReadBytes(inputStream, chunkid, 0, 4);
offset += 4;
}
first = false;
if (PngCsUtils.arraysEqual4(chunkid, ChunkHelper.b_IDAT))
{
skip = true; // extra dummy (empty?) idat chunk, it can happen, ignore it
}
else if (PngCsUtils.arraysEqual4(chunkid, ChunkHelper.b_IEND))
{
CurrentChunkGroup = ChunksList.CHUNK_GROUP_6_END;
endfound = true;
}
ReadChunk(chunkid, clen, skip);
}
if (!endfound)
{
throw new PngjInputException("end chunk not found - offset=" + offset);
}
// PngHelper.logdebug("end chunk found ok offset=" + offset);
}
/// <summary>
/// Constructs a PNGReader objet from a opened Stream
/// </summary>
/// <remarks>The constructor reads the signature and first chunk (IDHR)<seealso cref="FileHelper.CreatePngReader(string)"/>
/// </remarks>
///
/// <param name="inputStream"></param>
/// <param name="filename">Optional, can be the filename or a description.</param>
public PngReader(Stream inputStream, string filename)
{
this.filename = filename != null ? filename : string.Empty;
this.inputStream = inputStream;
this.chunksList = new ChunksList(null);
this.metadata = new PngMetadata(chunksList);
this.offset = 0;
// set default options
this.CurrentChunkGroup = -1;
this.ShouldCloseStream = true;
this.MaxBytesMetadata = 5 * 1024 * 1024;
this.MaxTotalBytesRead = 200 * 1024 * 1024; // 200MB
this.SkipChunkMaxSize = 2 * 1024 * 1024;
this.SkipChunkIds = new string[] { "fdAT" };
this.ChunkLoadBehaviour = Pngcs.Chunks.ChunkLoadBehaviour.LOAD_CHUNK_ALWAYS;
// starts reading: signature
byte[] pngid = new byte[8];
PngHelperInternal.ReadBytes(inputStream, pngid, 0, pngid.Length);
offset += pngid.Length;
if (!PngCsUtils.arraysEqual(pngid, PngHelperInternal.PNG_ID_SIGNATURE))
{
throw new PngjInputException("Bad PNG signature");
}
CurrentChunkGroup = ChunksList.CHUNK_GROUP_0_IDHR;
// reads first chunk IDHR
int clen = PngHelperInternal.ReadInt4(inputStream);
offset += 4;
if (clen != 13)
{
throw new System.Exception("IDHR chunk len != 13 ?? " + clen);
}
byte[] chunkid = new byte[4];
PngHelperInternal.ReadBytes(inputStream, chunkid, 0, 4);
if (!PngCsUtils.arraysEqual4(chunkid, ChunkHelper.b_IHDR))
{
throw new PngjInputException("IHDR not found as first chunk??? ["
+ ChunkHelper.ToString(chunkid) + "]");
}
offset += 4;
PngChunkIHDR ihdr = (PngChunkIHDR)ReadChunk(chunkid, clen, false);
bool alpha = (ihdr.Colormodel & 0x04) != 0;
bool palette = (ihdr.Colormodel & 0x01) != 0;
bool grayscale = (ihdr.Colormodel == 0 || ihdr.Colormodel == 4);
// creates ImgInfo and imgLine, and allocates buffers
ImgInfo = new ImageInfo(ihdr.Cols, ihdr.Rows, ihdr.Bitspc, alpha, grayscale, palette);
rowb = new byte[ImgInfo.BytesPerRow + 1];
rowbprev = new byte[rowb.Length];
rowbfilter = new byte[rowb.Length];
interlaced = ihdr.Interlaced == 1;
deinterlacer = interlaced ? new PngDeinterlacer(ImgInfo) : null;
// some checks
if (ihdr.Filmeth != 0 || ihdr.Compmeth != 0 || (ihdr.Interlaced & 0xFFFE) != 0)
{
throw new PngjInputException("compmethod or filtermethod or interlaced unrecognized");
}
if (ihdr.Colormodel < 0 || ihdr.Colormodel > 6 || ihdr.Colormodel == 1 ||
ihdr.Colormodel == 5)
{
throw new PngjInputException("Invalid colormodel " + ihdr.Colormodel);
}
if (ihdr.Bitspc != 1 && ihdr.Bitspc != 2 && ihdr.Bitspc != 4 && ihdr.Bitspc != 8 &&
ihdr.Bitspc != 16)
{
throw new PngjInputException("Invalid bit depth " + ihdr.Bitspc);
}
}