/// <summary>
/// Read the PNG image from the bytes.
/// </summary>
/// <param name="bytes">The bytes of the PNG data to be read.</param>
/// <param name="settings">Settings to apply when opening the PNG.</param>
/// <returns>The <see cref="Png"/> data from the bytes.</returns>
public static Png Open(byte[] bytes, PngOpenerSettings settings)
{
using (var memoryStream = new MemoryStream(bytes))
{
return(PngOpener.Open(memoryStream, settings));
}
}
/// <summary>
/// Read the PNG from the file path.
/// </summary>
/// <param name="filePath">The path to the PNG file to open.</param>
/// <param name="settings">Settings to apply when opening the PNG.</param>
/// <remarks>This will open the file to obtain a <see cref="FileStream"/> so will lock the file during reading.</remarks>
/// <returns>The <see cref="Png"/> data from the file.</returns>
public static Png Open(string filePath, PngOpenerSettings settings)
{
using (var fileStream = File.OpenRead(filePath))
{
return(Open(fileStream, settings));
}
}
public static Png Open(Stream stream, PngOpenerSettings settings)
{
if (stream == null)
{
throw new ArgumentNullException(nameof(stream));
}
if (!stream.CanRead)
{
throw new ArgumentException($"The provided stream of type {stream.GetType().FullName} was not readable.");
}
var validHeader = HasValidHeader(stream);
if (!validHeader.IsValid)
{
throw new ArgumentException($"The provided stream did not start with the PNG header. Got {validHeader}.");
}
var crc = new byte[4];
var imageHeader = ReadImageHeader(stream, crc);
var hasEncounteredImageEnd = false;
Palette palette = null;
using (var output = new MemoryStream())
{
using (var memoryStream = new MemoryStream())
{
while (TryReadChunkHeader(stream, out var header))
{
if (hasEncounteredImageEnd)
{
if (settings?.DisallowTrailingData == true)
{
throw new InvalidOperationException($"Found another chunk {header} after already reading the IEND chunk.");
}
break;
}
var bytes = new byte[header.Length];
var read = stream.Read(bytes, 0, bytes.Length);
if (read != bytes.Length)
{
throw new InvalidOperationException($"Did not read {header.Length} bytes for the {header} header, only found: {read}.");
}
if (header.IsCritical)
{
switch (header.Name)
{
case "PLTE":
if (header.Length % 3 != 0)
{
throw new InvalidOperationException($"Palette data must be multiple of 3, got {header.Length}.");
}
// Ignore palette data unless the header.ColorType indicates that the image is paletted.
if (imageHeader.ColorType.HasFlag(ColorType.PaletteUsed))
{
palette = new Palette(bytes);
}
break;
case "IDAT":
memoryStream.Write(bytes, 0, bytes.Length);
break;
case "IEND":
hasEncounteredImageEnd = true;
break;
default:
throw new NotSupportedException($"Encountered critical header {header} which was not recognised.");
}
}
read = stream.Read(crc, 0, crc.Length);
if (read != 4)
{
throw new InvalidOperationException($"Did not read 4 bytes for the CRC, only found: {read}.");
}
var result = (int)Crc32.Calculate(Encoding.ASCII.GetBytes(header.Name), bytes);
var crcActual = (crc[0] << 24) + (crc[1] << 16) + (crc[2] << 8) + crc[3];
if (result != crcActual)
{
throw new InvalidOperationException($"CRC calculated {result} did not match file {crcActual} for chunk: {header.Name}.");
}
settings?.ChunkVisitor?.Visit(stream, imageHeader, header, bytes, crc);
}
memoryStream.Flush();
memoryStream.Seek(2, SeekOrigin.Begin);
using (var deflateStream = new DeflateStream(memoryStream, CompressionMode.Decompress))
{
deflateStream.CopyTo(output);
deflateStream.Close();
}
}
var bytesOut = output.ToArray();
var(bytesPerPixel, samplesPerPixel) = Decoder.GetBytesAndSamplesPerPixel(imageHeader);
bytesOut = Decoder.Decode(bytesOut, imageHeader, bytesPerPixel, samplesPerPixel);
return(new Png(imageHeader, new RawPngData(bytesOut, bytesPerPixel, palette, imageHeader)));
}
}
/// <summary> /// Read the PNG image from the stream. /// </summary> /// <param name="stream">The stream containing PNG data to be read.</param> /// <param name="settings">Settings to apply when opening the PNG.</param> /// <returns>The <see cref="Png"/> data from the stream.</returns> public static Png Open(Stream stream, PngOpenerSettings settings) => PngOpener.Open(stream, settings);
