public Png(Stream s)
{
byte[] internalBuffer = new byte[8];
// Check header signature
s.Read(internalBuffer, 0, Signature.Length);
for (int i = 0; i < Signature.Length; i++)
{
if (internalBuffer[i] != Signature[i])
{
throw new InvalidDataException("Invalid PNG file - header signature mismatch");
}
}
// Load image
bool headerParsed = false;
bool isPaletted = false;
bool is24Bit = false;
RawList <byte> data = new RawList <byte>();
EmbeddedData = new Dictionary <string, string>();
while (true)
{
int length = ReadInt32BigEndian(s, ref internalBuffer);
s.Read(internalBuffer, 0, 4);
string type = Encoding.ASCII.GetString(internalBuffer, 0, 4);
if (!headerParsed && type != "IHDR")
{
throw new InvalidDataException("Invalid PNG file - header does not appear first");
}
int blockEndPosition = (int)s.Position + length;
switch (type)
{
case "IHDR": {
if (headerParsed)
{
throw new InvalidDataException("Invalid PNG file - duplicate header");
}
Width = ReadInt32BigEndian(s, ref internalBuffer);
Height = ReadInt32BigEndian(s, ref internalBuffer);
byte bitDepth = s.ReadUInt8(ref internalBuffer);
PngColorType colorType = (PngColorType)s.ReadUInt8(ref internalBuffer);
isPaletted = IsPaletted(bitDepth, colorType);
is24Bit = (colorType == PngColorType.Color);
var dataLength = Width * Height;
if (!isPaletted)
{
dataLength *= 4;
}
Data = new byte[dataLength];
byte compression = s.ReadUInt8(ref internalBuffer);
/*byte filter = */ s.ReadUInt8(ref internalBuffer);
byte interlace = s.ReadUInt8(ref internalBuffer);
if (compression != 0)
{
throw new InvalidDataException("Compression method (" + compression + ") not supported");
}
if (interlace != 0)
{
throw new InvalidDataException("Interlacing (" + interlace + ") not supported");
}
headerParsed = true;
break;
}
case "PLTE": {
Palette = new ColorRgba[256];
for (int i = 0; i < length / 3; i++)
{
byte r = s.ReadUInt8(ref internalBuffer);
byte g = s.ReadUInt8(ref internalBuffer);
byte b = s.ReadUInt8(ref internalBuffer);
Palette[i] = new ColorRgba(r, g, b);
}
break;
}
case "tRNS": {
if (Palette == null)
{
throw new InvalidDataException("Non-palette indexed images are not supported");
}
for (var i = 0; i < length; i++)
{
Palette[i].A = s.ReadUInt8(ref internalBuffer);
}
break;
}
case "IDAT": {
int newLength = data.Count + length;
data.Count = newLength;
s.Read(data.Data, newLength - length, length);
break;
}
case "tEXt": {
byte[] content = new byte[length];
s.Read(content, 0, length);
for (int i = 0; i < length; i++)
{
if (content[i] == 0)
{
string key = Encoding.ASCII.GetString(content, 0, i);
string value = Encoding.ASCII.GetString(content, i + 1, length - (i + 1));
EmbeddedData.Add(key, value);
break;
}
}
break;
}
case "IEND": {
using (var ms = new MemoryStream(data.Data)) {
ms.Position += 2;
using (var ds = new DeflateStream(ms, CompressionMode.Decompress, true)) {
int pxStride = (isPaletted ? 1 : (is24Bit ? 3 : 4));
int srcStride = Width * pxStride;
int dstStride = Width * (isPaletted ? 1 : 4);
byte[] buffer = new byte[srcStride];
byte[] bufferPrev = new byte[srcStride];
for (var y = 0; y < Height; y++)
{
// Read filter
PngFilter filter = (PngFilter)ds.ReadUInt8(ref internalBuffer);
// Read data
ds.Read(buffer, 0, srcStride);
for (var i = 0; i < srcStride; i++)
{
if (i < pxStride)
{
buffer[i] = UnapplyFilter(filter, buffer[i], 0, bufferPrev[i], 0);
}
else
{
buffer[i] = UnapplyFilter(filter, buffer[i], buffer[i - pxStride], bufferPrev[i], bufferPrev[i - pxStride]);
}
}
if (is24Bit)
{
for (var i = 0; i < buffer.Length / 3; i++)
{
Buffer.BlockCopy(buffer, 3 * i, Data, y * dstStride + 4 * i, 3);
Data[y * dstStride + 4 * i + 3] = 255;
}
}
else
{
Buffer.BlockCopy(buffer, 0, Data, y * dstStride, srcStride);
}
bufferPrev = buffer;
}
}
}
return;
}
default: {
//Console.WriteLine("Unknown PNG section: " + type);
s.Position += length;
break;
}
}
if (s.Position != blockEndPosition)
{
throw new InvalidDataException("Block " + type + " has incorrect length");
}
// Skip CRC
s.Position += 4;
}
}