Free online VSI to PNG converter

Olympus microscope software stores whole-slide images in VSI, while many image editors, browsers, and documentation systems accept PNG instead. Converting the file produces a portable raster image for sharing, annotation, web use, or basic editing, but it may represent only one selected slide view rather than the complete multi-resolution dataset.

What the VSI format is

VSI usually means Virtual Slide Image, a proprietary whole-slide microscopy format created by Olympus software such as cellSens and viewed with OlyVIA. It stores microscope imagery at multiple resolutions, often as tiled data, together with acquisition metadata.

A VSI dataset may include associated .ets files containing image data. Keep the .vsi file and its companion files in the same folder; opening only the VSI file can produce an incomplete image or missing-series error. If the extension came from software other than Olympus microscopy applications, identify that source first because VSI is not a universal single-purpose format.

What the PNG format is

PNG is a lossless, widely supported raster format. It preserves pixel values without the generation loss associated with JPEG and supports transparency, making it suitable for figures, screenshots, slide annotations, presentations, and web pages.

PNG does not preserve the VSI dataset structure, microscope metadata, focus levels, or resolution pyramid. A converted PNG is normally one rasterized image plane or one selected field of view.

How to convert VSI to PNG

Using Fiji and Bio-Formats

1. Install Fiji, which includes the Bio-Formats importer, and retain every file belonging to the VSI dataset in one folder.
2. Start Fiji and choose File → Open, then select the .vsi file. If Fiji asks to use Bio-Formats, accept it.
3. In Bio-Formats Import Options, select the required series. For a whole-slide file, choose the desired resolution level or region rather than loading the maximum-resolution slide if computer memory is limited.
4. For a full image or selected area, use Fiji’s crop or region-selection tools. Convert the display to RGB through Image → Type → RGB Color when the output must be a standard color PNG.
5. Choose File → Save As → PNG and save the result with a .png extension.

PNG export from Fiji generally saves the active image plane. If the import opened a stack, export the required slice or use an image-sequence workflow for multiple planes; do not expect one PNG file to contain the original VSI stack.

Using Olympus software

Open the dataset in OlyVIA or cellSens, select the required magnification and region, then use the application’s image export command, commonly found under File → Export or File → Save As. Choose PNG and set the export dimensions or resolution before saving. Menu names vary between Olympus product versions.

Converting online

You can convert the file for free on the 101convert.com website without installing software. Upload the complete VSI dataset when the converter requests associated files; a standalone .vsi file may not contain all image pixels. Online conversion is unsuitable for confidential patient or research data unless the site’s data-handling terms meet your requirements.

Quality and compatibility limitations

Choose the output resolution deliberately. Exporting a low-resolution overview creates a small PNG but removes fine cellular detail; exporting a full-resolution whole slide can create a very large image that exceeds PNG, browser, or application limits.

PNG supports 8-bit and 16-bit grayscale and RGB data, but ordinary viewers may display 16-bit images incorrectly or reduce them to 8-bit. For routine color figures, RGB PNG is the most compatible choice. Preserve the original VSI files when metadata, calibration, z-stacks, multiple focal planes, or future reprocessing matters.