int ReadRowRaw(int nrow) { if (nrow == 0 && FirstChunksNotYetRead()) { ReadFirstChunks(); } if (nrow == 0 && interlaced) { System.Array.Clear(rowb, 0, rowb.Length); // new subimage: reset filters: this is enough, see the swap that happens lines } // below int bytesRead = ImgInfo.BytesPerRow; // NOT including the filter byte if (interlaced) { if (nrow < 0 || nrow > deinterlacer.getRows() || (nrow != 0 && nrow != deinterlacer.getCurrRowSubimg() + 1)) { throw new PngjInputException($"invalid row in interlaced mode: { nrow }"); } deinterlacer.setRow(nrow); bytesRead = (ImgInfo.BitspPixel * deinterlacer.getPixelsToRead() + 7) / 8; if (bytesRead < 1) { throw new PngjExceptionInternal("what's going on??"); } } else { // check for non interlaced if (nrow < 0 || nrow >= ImgInfo.Rows || nrow != rowNum + 1) { throw new PngjInputException($"invalid row: { nrow }"); } } rowNum = nrow; // swap buffers byte[] tmp = rowb; rowb = rowbprev; rowbprev = tmp; // loads in rowbfilter "raw" bytes, with filter PngHelperInternal.ReadBytes(idatIstream, rowbfilter, 0, bytesRead + 1); offset = iIdatCstream.GetOffset(); if (offset < 0) { throw new PngjExceptionInternal($"bad offset ?? { offset }"); } if (MaxTotalBytesRead > 0 && offset >= MaxTotalBytesRead) { throw new PngjInputException($"Reading IDAT: Maximum total bytes to read exceeeded: { MaxTotalBytesRead } offset:{ offset }"); } rowb[0] = 0; UnfilterRow(bytesRead); rowb[0] = rowbfilter[0]; if ((rowNum == ImgInfo.Rows - 1 && interlaced == false) || (interlaced && deinterlacer.isAtLastRow())) { ReadLastAndClose(); } return(bytesRead); }
/// <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); } }