creating tiles of 16bit multiband (4 band) tiff image leaves black canvas about pyvips HOT 4 OPEN

Hello @Rjaat, I'd guess your TIFF is not using 0-65535 for black to white. When it's converted to 8-bit PNG, it looks black but isn't.

You'd need to share a sample source image before anyone could say more.

Are you sure you need that huge overlap?

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Thanks @jcupitt for your reply.

png tile information:

Width	1280
Height	1280
Data type	UInt16 - Sixteen bit unsigned integer
GDAL Driver Description	PNG

While making chunk of 4 band 16bit images the png tiles also generated in 16bit format which is not being rendered by openseadragon viewer. The same is also true when I have 3 band 16 bit image.

In another scenario where I have 8 bit RGB images everything works fine.

Yes, we need 50% overlap in our scenario

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As I said, it seems to work for me. You need to share a sample image so I can try to reproduce your problem.

For example, I can take this sample RGBA image:

Make a 16-bit, four band TIFF like this:

vips colourspace biglion.png x.tif rgb16

dzsave like this:

vips dzsave x.tif x --suffix .png --tile-size 640 --overlap 320

And I see tiles like this:

$ vipsheader x_files/11/1_1.png 
x_files/11/1_1.png: 1280x1280 ushort, 4 bands, rgb16, pngload

Which seems correct.

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Oh, do you want it to write 8-bit PNG tiles? You need to convert before dzsave, perhaps:

image = pyvips.Image.new_from_file(image_path, access='sequential')

image \
    .colourspace('srgb') \
    .dzsave(
        "basename",  # Base name for the output files
        suffix=".png",  # Sets the format of the tiles; use '.jpg' for JPEG tiles
        overlap=320,  # The overlap between tiles; adjust as necessary
        tile_size=640  # The size of each tile in pixels
    )

Are you sure you need random? I think sequential should work, even with very large overlaps, and will be much faster.

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