How Tantalum turns photos into an Instagram carousel or a vertical video
The Tantalum slideshow exporter fits each photo to 1080 by 1080, 1080 by 1350 or 1080 by 1920, writes a three-slide carousel from one image or from three, and renders an MP4 with ffmpeg or falls back to frames.
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A photo from a camera is rarely the right shape for a social feed, which wants a few fixed proportions. Tantalum's slideshow view does the fitting before the file leaves the application, so the crop is the photographer's decision and not the platform's.
Three sizes
The exporter has three targets, each with a fixed pixel size:
| Target | Size | Ratio |
|---|---|---|
| Instagram square | 1080 by 1080 | 1:1 |
| Instagram portrait | 1080 by 1350 | 4:5 |
| Instagram and TikTok Reels | 1080 by 1920 | 9:16 |
Fitting a photo to a frame
Each photo is scaled to cover the frame. The scale factor is the larger of the width ratio and the height ratio, so the picture always fills the frame in both directions, and it is then centred. Whatever hangs over the edge on the long side is cropped. There are no bars at the sides or the top, and that is the intended behaviour: the frame is filled and the crop is centred.
The scaling uses SkiaSharp's high quality filter.
A carousel from one photo or from three
A carousel post is built from exactly three slides. The exporter takes the images you give it and does one of two things:
- One image
- The photo is cut into three vertical panels, so swiping through the carousel pans across a single wide picture.
- Two or more images
- One slide is made from each of the first three photos.
The slides are saved as JPEG files at quality 92, named instagram_carousel_01, 02 and 03, in the output folder you chose. If you give it no images, it asks you to add at least one.
A video
For a video, each photo is held on screen for the number of seconds you set. The exporter renders the video at 30 frames per second, so a photo shown for three seconds becomes 90 identical frames. Frames are written as PNG files to a temporary folder, then assembled into an MP4 with ffmpeg.
If ffmpeg is not installed, the exporter does not fail. It falls back to writing the frames into a folder of PNGs next to where the video would have gone, named after it with _frames on the end, and tells you so. You can assemble them with any tool you like later.
Photos that cannot be decoded are skipped. If none of them can be decoded, the export reports that and stops.
Plain files out
The output is ordinary JPEG, PNG and MP4 files at the platform sizes. They can be looked at before anything is posted, opened in other tools and kept, and posting them does not need Tantalum.
Tantalum is a Windows desktop application. The current download is on the Tantalum page.
Written by Caisson AI. Questions or corrections go to hello@caissonai.co.