Apple Watch Ultra 4 screenshot size: 422x514 from Sume

App Store Connect lists 422 x 514 pixels for Apple Watch Ultra 4 and Ultra 3. Sume's image API cannot return that size directly: the documented custom image_size rule for ChatGPT Image 2.5 has a 655,360-pixel minimum, and every watch size is far below it. The route that can hit the exact pixels is a Timeline render of a still at that width and height, then a png frame from video_frames.

Apple's page, read 2026-10-01, lists six watch sizes and says to use the same size consistently across all localizations. Sume's limits are from https://docs.sume.com/models/images, https://docs.sume.com/models/timeline and https://docs.sume.com/models/video-frames.

Which Apple Watch screenshot sizes does Apple list?

Apple lists one of six sizes, depending on the watch model you target. Pick one and keep it across every localization.

Why can't the image API make a watch screenshot?

The custom image_size rule documented for ChatGPT Image 2.5 has three parts: both edges multiples of 16, a maximum edge of 3840 with aspect at most 3:1, and 655,360-8,294,400 pixels. The largest watch size, 422 x 514, is 216,908 pixels, so even the two sizes whose edges are multiples of 16 (416 x 496 and 368 x 448) fall under the pixel floor.

See the image size and aspect ratio post for the preset list.

How do I get exact watch pixels from Sume?

Timeline video[].source_url accepts a Sume-hosted still, and stills are static holds. Set output.width and output.height to the watch size (all six are even and inside 256-2160), set audio.mode to silence with a short duration_seconds, and render. Then call video_frames with at inside the clip and format set to png; leaving max_edge out keeps the source size.

Set video[].fit deliberately. The default is cover, which crops a source with a different aspect ratio. A watch screenshot is close to 4:5, so supply a source that already matches, or use contain or blur. Check the frame size before you upload.

The how-to for frame extraction is in extract video frames.

What does Sume not do here?

Sume does not check your art against Apple's content rules, and the docs do not describe a screenshot-specific export. Apple's page also says images cannot include alpha channels or transparencies, so confirm the final PNG before upload. A generated UI mockup is still a picture, not a capture of your app, so check it matches what the app shows.