Hjg.Pngcs.PngWriter.WriteSignatureAndIHDR C# (CSharp) Method

        private void WriteSignatureAndIHDR()
        {
            CurrentChunkGroup = ChunksList.CHUNK_GROUP_0_IDHR;
            PngHelperInternal.WriteBytes(outputStream, Hjg.Pngcs.PngHelperInternal.PNG_ID_SIGNATURE); // signature
            PngChunkIHDR ihdr = new PngChunkIHDR(ImgInfo);
            // http://www.libpng.org/pub/png/spec/1.2/PNG-Chunks.html
            ihdr.Cols = ImgInfo.Cols;
            ihdr.Rows = ImgInfo.Rows;
            ihdr.Bitspc = ImgInfo.BitDepth;
            int colormodel = 0;
            if (ImgInfo.Alpha)
                colormodel += 0x04;
            if (ImgInfo.Indexed)
                colormodel += 0x01;
            if (!ImgInfo.Greyscale)
                colormodel += 0x02;
            ihdr.Colormodel = colormodel;
            ihdr.Compmeth = 0; // compression method 0=deflate
            ihdr.Filmeth = 0; // filter method (0)
            ihdr.Interlaced = 0; // never interlace
            ihdr.CreateRawChunk().WriteChunk(outputStream);
        }