Chrome Web Store screenshots at 1280x800: request it directly

Chrome Web Store screenshots can be 1280x800 (or 640x400), and 1280x800 is a legal GPT Image 2.5 custom size on Sume: both edges are multiples of 16 (80 x 16 and 50 x 16) and it has 1,024,000 pixels. Request it with image_size: "1280x800". A generated picture is a mockup, so show your own real UI in the screenshot.

Chrome's figures are from its Web Store images page; the rules from OpenAI's guide and the Sume Image API docs. Read 2026-10-01; the arithmetic is ours.

What does the store require?

Per Chrome's page: 1 to 5 screenshots, 1280x800 preferred (640x400 also allowed), JPG or PNG, with square corners and full-bleed artwork.

Does 1280x800 pass?

OpenAI's guide lists the GPT Image 2.5 custom-size rules: both edges multiples of 16, edges at most 3840, aspect ratio between 1:3 and 3:1, and 655,360 to 8,294,400 total pixels. Sume's Image API docs state the same limits for image_size on GPT models.

What do I send?

Ask for full-bleed artwork with no rounded corners or border, as Chrome requires.

curl -X POST https://api.sume.com/v1/images \
  -H "Authorization: Bearer $SUME_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "openai/gpt-image-2.5",
    "prompt": "Full-bleed product screenshot style: clean dashboard with a left sidebar and bar chart, flat, square corners, no frame",
    "image_size": "1280x800",
    "output_format": "png"
  }'

Do I need the 640x400 size?

No. If you do need it, generate 1280x800 and halve it yourself; 640x400 is below the GPT pixel floor.