/// <summary>
/// Function to load an image from a stream.
/// </summary>
/// <param name="stream">The stream containing the image data to read.</param>
/// <param name="size">The size of the image within the stream, in bytes.</param>
/// <returns>A <see cref="IGorgonImage"/> containing the image data from the stream.</returns>
/// <exception cref="GorgonException">Thrown when the image data in the stream has a pixel format that is unsupported.</exception>
protected override IGorgonImage OnDecodeFromStream(Stream stream, long size)
{
var wic = new WicUtilities();
Stream streamAlias = stream;
try
{
// If we have a stream position that does not begin exactly at the start of the stream, we have to wrap that stream in a
// dummy stream wrapper. This is to get around a problem in the underlying COM stream object used by WIC that throws an
// exception when the stream position is not exactly 0.
if (streamAlias.Position != 0)
{
streamAlias = new GorgonStreamWrapper(stream, 0, size);
}
IGorgonImage result = wic.DecodeImageData(streamAlias, size, SupportedFileFormat, DecodingOptions, FrameOffsetMetadataNames);
if (result == null)
{
throw new IOException(string.Format(Resources.GORIMG_ERR_FILE_FORMAT_NOT_CORRECT, Codec));
}
if (stream.Position != streamAlias.Position)
{
stream.Position += streamAlias.Position;
}
return(result);
}
finally
{
if (streamAlias != stream)
{
streamAlias?.Dispose();
}
wic.Dispose();
}
}
public void StreamWrapperTest()
{
byte[] block1 =
{
0,
1,
2,
3,
4,
5,
6,
7,
8,
9,
10
};
using (MemoryStream stream = new MemoryStream())
{
stream.Write(block1, 0, block1.Length);
stream.Position = 0;
using (GorgonStreamWrapper wrapper = new GorgonStreamWrapper(stream, 6, 5))
{
byte[] actualBytes = new byte[5];
Assert.AreEqual(5, wrapper.Read(actualBytes, 0, 5));
for (int i = 0; i < actualBytes.Length; ++i)
{
Assert.AreEqual(block1[i + 6], actualBytes[i]);
}
Assert.AreEqual(wrapper.Length, wrapper.Position);
}
Assert.AreEqual(0, stream.Position);
using (GorgonStreamWrapper wrapper = new GorgonStreamWrapper(stream, 6, 5))
{
byte[] actualBytes = new byte[8];
Assert.AreEqual(5, wrapper.Read(actualBytes, 0, 8));
}
using (GorgonStreamWrapper wrapper = new GorgonStreamWrapper(stream, 2))
{
byte[] actualBytes = new byte[3];
wrapper.Seek(3, SeekOrigin.Begin);
wrapper.Read(actualBytes, 0, 3);
for (int i = 0; i < actualBytes.Length; ++i)
{
Assert.AreEqual(block1[i + 5], actualBytes[i]);
}
wrapper.Seek(-3, SeekOrigin.End);
wrapper.Read(actualBytes, 0, 3);
for (int i = 0; i < actualBytes.Length; ++i)
{
Assert.AreEqual(block1[block1.Length - 3 + i], actualBytes[i]);
}
}
}
}
