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I have a huge 8 bit B&W image (PNG, 200k x 100k px) which is a high resolution generated map of a large area, so I can't generate it in small chunks. The map is fine, Photoshop CC 19 (Windows 10) handles it great, but I now need to slice it into 8192 x 8192 px tiles, and I'm having no luck. Nothing in the "save as" dialog, nor anything apparently relevant in the "export as" dialog, and "save for web" is greyed out and I can't figure why.

Clean install, from Adobe installer, no messing round or extensions. I've got as far as an image with slices/tiles shown correctly in blue (and unwanted slices/tiles deleted), but can't seem to get it to do anything with them.

I've even tried as Adobe says, selecting a tile and edit->copy (to paste into another tab or even MS Paint), but it copies the entire image, not just the content of that tile.

I tried using ImageMagick instead, but it failed with a "can't access magic.xml" error for reasons I don't understand, so I'm back trying to slice it in Photoshop.

Any ideas, workarounds, or similar, whatsoever? Speed is key - all I need to do is slice, but I've got to upload them for a presentation tomorrow morning! :)

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2 Answers 2

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It seems that the maximum size allowed in Photoshop for Save for Web is 30000 px.

You will have to divide your image into 25k x 25k documents and then do the save for web with the slices.

What I would do is:

  • Create a selection frame with a fixed size: width=24576px, height=24576px
  • Click on the top-left corner
  • Menu Image > Crop
  • Proceed to save for web all the slices in this part of the image
  • Then Undo and do the same with the next image parts
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  • "Save for web" doesn't seem to exist in CC19..... can you edit the answer to whatever the equivalent is in Photoshop these days, as I can't find anything that does it. Also that's something like 30 manual croppings, all pixel exact, it would work as a once of for the demo, presentation but isn't sustainable, what would be the right way to handle this longer term (Photoshop says it handles slices at least 8kx8k which is plenty for the slices I'm doing)
    – Stilez
    Aug 20, 2018 at 8:31
  • Menu File > Export > Save for Web
    – user120647
    Aug 20, 2018 at 10:04
  • as the Q states: "....save for web" is greyed out and I can't figure why."
    – Stilez
    Aug 21, 2018 at 5:18
  • Indeed, the source image cannot exceed 30K px, however there is an even stricter limit to the output image too, which is 8192px :(
    – David Salamon
    Nov 15, 2022 at 12:35
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In Windows 10, Photoshop CC 19.1.5, save for web is still available under File > Export > Save for Web (Legacy).

If Save for Web is greyed out, then something else is up. Possibly the image is in 32bit per channel. Save for Web doesn't work with that bit depth. It will only work in 8bit per channel or 16bit bit per channel.

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  • The image is PNG 8bit. Checked + confirmed. I agree its likely something else is up - but what could it be?
    – Stilez
    Aug 21, 2018 at 5:19
  • Perhaps because the image is too big, as Danielillo has said
    – Billy Kerr
    Aug 21, 2018 at 7:34
  • Adobe say a photo can be upto 300k each side (and has no problem working with the pic I'm using), and slices must be under up to 8192; I'm within those limits. Which other limits might be exceeded?
    – Stilez
    Aug 21, 2018 at 8:27
  • What colour mode is the image in? "Multichannel" mode also greys out save for web.
    – Billy Kerr
    Aug 21, 2018 at 8:35

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