Printful print file requirements and what to ask Sume for

What print file does Printful require?

Printful's print-file page, written for posters and canvas wall art, asks for a PNG or JPEG in the sRGB IEC61966-2.1 color profile, full-bleed over the whole print area. It calls 300 DPI the ideal resolution, accepts a minimum of 75 DPI, and says the Design Maker default is 150 DPI.

The page does not give maximum file sizes or exact pixel dimensions; it says to check the file guidelines on the product page and download the print file template. Those product-level numbers are therefore not stated here.

The page's specification

The page describes PNG for designs with transparency or detailed graphics and JPEG for simpler graphics.

Turning DPI into pixels

Pixels equal print inches times DPI. A product that prints 10 by 8 inches would need 3000 by 2400 pixels at 300 DPI and 1500 by 1200 at 150 DPI; take the real inches from Printful's template, not from this example.

On ChatGPT Image 2.5, custom sizes are capped at a 3840 maximum edge and 8,294,400 total pixels, and 3000 by 2400 is 7,200,000, which fits. Larger prints exceed that ceiling, so plan for upscaling outside the generation call or a lower DPI. The Sume docs describe Nano Banana 2 tiers of 0.5K, 1K, 2K and 4K without listing pixel counts on the Image API page, so measure what you get.

What to ask Sume for

Ask for a PNG, the aspect ratio of the print area, and the highest resolution tier the model lists. For an artwork with a cutout design, ChatGPT Image 2.5 can return a transparent background with background: transparent. Sume's output formats are png, jpeg, webp and svg, matching Printful's PNG and JPEG.

``json { "model": "google/nano-banana-2", "prompt": "Poster artwork, full bleed, no border, no text", "aspect_ratio": "4:5", "resolution": "4K", "output_format": "png" } ``

Tagging the file as sRGB and setting DPI are not request fields on the Image API; do both in your export step and compare with the template. The existing guide AI image for print at 300 DPI covers the same workflow in more depth.