How to split an image into a grid or carousel

The maths that decides whether the seams show, and the upload order that decides whether the picture is the right way round.

Two different things

A grid post is one picture cut into tiles that are posted separately and sit next to each other on your profile, forming the whole image again. Three across is the usual shape, since profiles are three columns wide; nine tiles is a full 3×3 block.

A carousel is one wide picture cut into slides that read as continuous as you swipe. The picture is never assembled in one view — it moves past you.

They need different cuts, and a grid tile is not a carousel slide.

Why the pieces must tile exactly

Here is the failure that makes most splitters unusable, and it only shows up on some images.

Take a 1080-pixel square and cut it into three: 360 pixels each, no problem. Now take 1081 pixels. Divided by three that is 360.33 per tile. Round it down to 360 and three tiles cover 1080 pixels — the last column of your photograph has been thrown away. Round up to 361 and they cover 1083, so a column gets repeated.

One pixel sounds like nothing. On a profile grid, where the tiles sit against each other with hairline gaps, a missing or duplicated column shows as a visible seam running through the picture — and on a face or a straight line it is unmistakable. It is also invisible while you are working, because you are looking at tiles individually, and obvious the moment all nine are posted.

The fix is to stop thinking about tile width. Work out where each boundary falls across the whole image, round each boundary once, and take each tile as the space between two of them. The tiles then come out 360, 361 and 360 — unequal by a pixel, and together covering the original exactly, with nothing lost and nothing repeated.

That is why the splitter sometimes tells you your tiles are different widths. It is not a fault; it is the reason the picture survives.

The posting order everybody gets wrong

A profile grid fills from the top left, reading across and down. But posts appear newest first. So the tile that belongs in the top-left corner has to be posted last, and the bottom-right tile goes up first.

Get it wrong and the picture appears mirrored and inverted, and there is no fix except deleting every post and starting again. Every tile the splitter produces is named with its upload order for exactly this reason: post them in filename order and it comes out right.

One more thing: post them in reasonably quick succession. A grid that is half-finished for a day looks like a mistake to anyone visiting your profile.

Getting a carousel to look continuous

Feeds crop carousel slides to a fixed shape, so the width of your source has to suit the number of slides you want. If it does not, the platform trims each slide — usually taking a strip off the top and bottom — and the picture no longer lines up across the swipe.

Work backwards: decide the slide shape, multiply its width by the number of slides, and make the source that wide. For three slides at the tallest portrait shape a feed keeps, that is a source three times the slide width. The splitter works this out and tells you when your image is the wrong width for the number of slides you asked for.

Before you cut

Do any colour work, cropping and text on the whole image, not on the tiles. Anything applied per tile will not match across the seams, and a gradient or a vignette applied nine times is nine slightly different gradients.

Resize the whole picture to its final dimensions first, too. Cutting first and resizing the pieces afterwards reintroduces the rounding problem, one tile at a time.

Frequently asked questions

Why are my tiles different widths?

Because the image does not divide evenly. A 1081-pixel width cut into three gives 360, 361 and 360 — and that is what allows the tiles to cover the whole picture. Forcing them all to the same width would drop or repeat a pixel column, which shows as a seam.

What order do I post grid tiles in?

Backwards. The grid fills from the top left but posts appear newest first, so the top-left tile is posted last. The files are named in upload order, so posting them in filename order gives the right result.

What size should the original image be?

For a 3×3 grid, a square whose width divides sensibly by three — 1080 or 1440 works well. For a carousel, the slide width multiplied by the number of slides. Bigger than needed is fine; smaller means the platform enlarges it, which looks soft.

Can I split a picture I already posted?

You can split any image file you have. You cannot download someone else's post to split it, and this tool does not do that.

Will the platform recompress the tiles?

Yes, every platform re-encodes what you upload. That is why exporting at maximum quality achieves little — being the right size and cut correctly matters far more.

Are my images uploaded?

No. The image is read and cut in your browser using the canvas, and every download is generated on your device.