We have checked the code snippet that you shared and noticed that you were using GifDevice to generate TIFF images. Please note that TiffDevice is offered by Aspose.PDF in order to generate TIFF images.
We tested the scenario using following code snippet with Aspose.PDF for .NET 20.1 and were unable to notice any issue. Would you kindly try using following code snippet with latest version of the API and in case you still face any issue, please let us know. For your kind reference, output TIFF images are also attached.
using (FileStream imageStream = new FileStream(dataDir + page.Number.ToString("000") + ".tiff", FileMode.Create))
TiffSettings tiffSettings = new TiffSettings()
Compression = CompressionType.LZW,
Depth = ColorDepth.Format8bpp
// Create TIFF device
TiffDevice tiffDevice = new TiffDevice(resolution, tiffSettings)
RenderingOptions = new RenderingOptions
SystemFontsNativeRendering = true,
UseNewImagingEngine = true
// Convert a particular page and save the image to stream
tiffDevice.Process(pdfDocument, page.Number, page.Number, imageStream);
outputtiff.zip (1.0 MB)