protected virtual void ValidateReturnStream(OptimizerArgs args, Stream originalStream)
{
args.IsOptimized = false; // Assume its not by default
if (args.Stream != null && args.Stream.Length > 0)
{
if (args.Stream is FileStream)
{
throw new InvalidOperationException($"{GetType().Name} returned a FileStream. This will leave orphaned files on disk after the stream is disposed. Don't do that. Return files as pre-buffered memory streams.");
}
if (!args.Stream.CanSeek)
{
throw new InvalidOperationException($"{GetType().Name} returned a non seekable stream. This is not allowed. Try buffering it into a memory stream first.");
}
if (!args.Stream.CanRead)
{
args.AddMessage($"{GetType().Name} returned a non readable stream. This probably means it failed after disposing the input stream. We will keep the original stream.");
args.Stream = originalStream;
}
// seek to the start so the next processor, if there is one, gets a clean stream
args.Stream.Seek(0, SeekOrigin.Begin);
if (args.Stream.Length > originalStream.Length)
{
args.AddMessage($"{GetType().Name}: the optimized image resulted in a larger file size ({args.Stream.Length} vs {originalStream.Length}). Using the original instead.");
args.Stream.Dispose();
args.Stream = originalStream;
}
else if (args.Stream.Length == originalStream.Length)
{
args.AddMessage($"{GetType().Name}: the optimized image resulted in the same file size ({args.Stream.Length}). Using the original instead.");
args.Stream.Dispose();
args.Stream = originalStream;
}
else
{
originalStream.Dispose();
args.IsOptimized = true;
}
}
else
{
if (args.Stream == null)
{
args.AddMessage($"{GetType().Name} returned a null stream. This probably means it failed. We will keep the original stream.");
}
else
{
args.AddMessage($"{GetType().Name} returned a zero length stream. This probably means it failed. We will keep the original stream.");
}
args.Stream = originalStream;
}
}
// NOTE: IT IS EXPECTED THAT ANY PROCESSOR WILL DISPOSE OF THE INPUT STREAM ONCE IT CONSUMES IT
// Throw an exception if you have a processing error.
public virtual void Process(OptimizerArgs args)
{
if (!ValidateInputStream(args))
{
return;
}
var originalStream = new MemoryStream();
// if we cannot seek the stream, we buffer it into a memory stream so we can seek it
// this can occur if getting an unresized image in the getMediaStream pipeline
if (!args.Stream.CanSeek)
{
var bufferedStream = new MemoryStream();
args.Stream.CopyTo(bufferedStream);
args.Stream.Dispose();
args.Stream = bufferedStream;
}
try
{
// buffer the original stream to memory, so that if optimization fails to save file size we can back it out easily
// and keep the original stream
args.Stream.Seek(0, SeekOrigin.Begin);
args.Stream.CopyTo(originalStream);
originalStream.Seek(0, SeekOrigin.Begin);
args.Stream.Seek(0, SeekOrigin.Begin);
ProcessOptimizer(args);
ValidateReturnStream(args, originalStream);
}
catch (Exception ex)
{
args.IsOptimized = false;
args.Stream.Dispose();
args.Stream = originalStream;
Log.Error($"Dianoga: Unable to optimize {args.MediaPath} due to a processing error! It will be unchanged.", ex, this);
}
}
protected virtual bool ValidateInputStream(OptimizerArgs args)
{
return(args.Stream != null && args.Stream.CanRead);
}
protected abstract void ProcessOptimizer(OptimizerArgs args);
