I have been unable to save TIFFs in any compression format other than LZW using the Conversion API. I've tried G4 and RLE but it always appears to result in an LZW TIFF. G3 or G4 would be the best option for us but LZW is, unfortunately, the worst option in our case.
I'm setting TiffOptions.Compression to various members of the enumeration.
Here's the complete code I'm using in case I'm making some kind of mistake:
var options = new NamedValueCollection(parameters.Options);
var outputType = options.GetValue("OutputFileFormat", "image/tiff");
var config = new ConversionConfig();
var conv = new ConversionHandler(config);
var imageSaveOptions = new ImageSaveOptions
{
ConvertFileType = GetConvertFileType(outputType),
OutputType = OutputType.Stream, // Using streaming for the result. See comment below.
PageMode = false, // false seems to indicate to put all pages in a single file. Docs said it defaults to false--it doesn't.
Grayscale = options.GetValue("MakeGrayScale", true), // Let's go grayscale for now. TODO: Maybe another option?
CustomName = Path.GetFileName(parameters.Target.File), // When creating an output file in OutputPath, it used this name. We're not using that option but the docs implied
// it may created a cached file so I wanted the name to be unique and identifiable if there are later issues.
TiffOptions = new TiffOptions { Compression = options.GetValue("Compression", TiffOptions.TiffCompression.Ccitt4) }
};
var loadOptions = new LoadOptions();
using (var source = File.OpenRead(parameters.Source.File)) // Don't use the file name as a source or it will assume the format based on the extension. Use a stream to hide the extension so they make no assumption.
{
using (var destination = File.OpenWrite(parameters.Target.File))
{
// Tell it to return a stream by setting the ImageSaveOptions.OutputType to Stream
// and then call the generic function with a Stream type param. The other option is string in which case it puts it in the
// CoversionConfig.OutputPath folder but that had two issues: yet another file to delete and the function often returned null
// instead of said path. I'm not sure what I was doing wrong but the stream version has been reliable without further research.
using (var result = conv.Convert(source, loadOptions, imageSaveOptions))
{
// Transfer from the returned stream to the destination file.
foreach (var chunk in result.GetChunks(16384))
destination.Write(chunk, 0, chunk.Length);
}
}
}
Thanks
-Jonathan