Free online NDPI to TIFF converter

NDPI files are whole-slide images produced by Hamamatsu NanoZoomer scanners, but many image editors, laboratory systems, and archive workflows expect TIFF. Converting to TIFF makes the image easier to open, process, and share, although a full-resolution slide may require BigTIFF and substantial storage.

What the NDPI format is

NDPI is Hamamatsu’s proprietary whole-slide image format. NanoZoomer scanners store microscope slides as very large, multi-resolution images with associated metadata, thumbnails, and sometimes label images. You may encounter NDPI files when receiving digital pathology scans or exporting slides from Hamamatsu NDP.view2.

NDPI is TIFF-like internally, but ordinary TIFF software may not understand its proprietary structure. OpenSlide, Fiji with Bio-Formats, QuPath, and Hamamatsu software can read many NDPI variants. Support depends on the scanner generation, compression, and file contents.

What the TIFF format is

TIFF is a widely supported raster-image format used in microscopy, scanning, publishing, image analysis, and archival workflows. It supports lossless compression such as LZW, Deflate, and Zstandard, tiled storage, multiple pages, metadata, and the BigTIFF extension for files larger than 4 GB.

TIFF is useful when the destination application cannot open NDPI or when an image must be processed in software such as ImageJ, Photoshop, or a laboratory analysis system. A conventional TIFF export is often a single selected resolution or region, not the complete multi-resolution slide structure contained in the NDPI file.

How to actually convert NDPI to TIFF

Using 101convert online

You can convert the file for free on the 101convert.com website without installing software. Upload the NDPI file, select TIFF as the output format, start the conversion, and download the result. This is suitable for files accepted by the service; very large whole-slide images may exceed upload, processing, or output limits, and patient-sensitive slides should only be uploaded where the required privacy controls are available.

Using Fiji and Bio-Formats

1. Install Fiji, which includes ImageJ, then add or update the Bio-Formats plugin through Help → Update.
2. Open the file through File → Open or Plugins → Bio-Formats → Bio-Formats Importer.
3. In the importer dialog, select the required resolution series and avoid opening the full-resolution level if the computer lacks sufficient RAM.
4. Save the opened image with File → Save As → TIFF.

Fiji exports the selected image plane or resolution. It may not preserve the NDPI pyramid, scanner annotations, or all proprietary metadata. For a manageable export, choose a lower-resolution series or export only the region needed for analysis.

Using OpenSlide and Python

OpenSlide reads the resolution levels in an NDPI slide. The following example exports one complete resolution level as an RGB TIFF:

pip install openslide-python tifffile numpy

from openslide import OpenSlide
import numpy as np
import tifffile

slide = OpenSlide('sample.ndpi')
level = 2
width, height = slide.level_dimensions[level]
image = slide.read_region((0, 0), level, (width, height)).convert('RGB')
tifffile.imwrite('sample_level2.tif', np.asarray(image), photometric='rgb', compression='zlib')
slide.close()

Change level to select another pyramid level; level 0 is the highest available resolution. The selected level is loaded into memory as one array, so exporting a full-resolution slide can exhaust RAM. For large slides, process rectangular regions in tiles or export a lower level. If the output exceeds 4 GB, use BigTIFF where supported by the target application, for example by adding bigtiff=True to tifffile.imwrite.

Quality, compatibility, and limitations

• Converting does not improve the source image. If the NDPI contains JPEG-compressed scanner data, TIFF export cannot restore detail lost during scanning.
• A TIFF export may discard the NDPI resolution pyramid, focus data, scanner calibration, annotations, macro images, and proprietary metadata. Keep the original NDPI as the archival master.
• Use lossless TIFF compression such as Deflate or LZW when further analysis is required. Avoid JPEG TIFF compression for measurements or repeated editing.
• Whole-slide TIFFs can be tens or hundreds of gigabytes at full resolution. Tiled BigTIFF or OME-TIFF is generally more practical than a single untiled TIFF, but compatibility varies between applications.
• Confirm the pixel dimensions, micrometers-per-pixel calibration, color profile, and orientation after conversion; these values may not transfer automatically.