AI Image Upscaler for Print: upscale images to 300 DPI for print on demand and KDP

Upscale images for print with AI. Turn small or low-quality designs into print-ready files at the exact size each print-on-demand platform asks for: a 1024 px AI-art PNG becomes a 4500 x 5400 px, 300 DPI transparent PNG under 25 MB for Merch by Amazon, and the same run can output Redbubble, TeePublic, Printful, Printify, Etsy wall-art and KDP cover sizes. Real-ESRGAN upscaling (commercial use allowed), halo-free transparency, sRGB conversion and automatic file-size fitting.

The tool AI-upscales with Real-ESRGAN. Its BSD-3-Clause license allows commercial use. Then it does the fiddly parts that generic upscalers skip:

• Exact platform sizes. Amazon Merch, Redbubble (12 products), TeePublic, Printful, Printify, Etsy printable wall art (8×10 to 24×36 in, A4–A2), Kindle eBook covers, and a KDP paperback cover calculator (trim size + page count + paper → full-wrap size with bleed, as a PDF).
• Transparency done right. The alpha channel is upscaled by AI too, so cut-out edges stay crisp. Colours are bled under transparent pixels, so you get no dark or white halos around your design on a coloured shirt.
• Correct print metadata. The DPI is written into the file, colours are converted to sRGB (CMYK, Adobe RGB and other ICC profiles are handled), and an sRGB profile is embedded. Camera and editor metadata is stripped (optional).
• File-size limits. The tool compresses until the file fits (Merch's 25 MB by default, or any limit you set). PNG gets maximum lossless compression first, then an optional 256-colour reduction. JPG and PDF use the highest quality that fits.
• Fit modes. Contain keeps the whole design and pads with transparency. Cover fills the canvas and crops. Exact stretches. Alignment can be top, center or bottom. Empty transparent margins are trimmed automatically for apparel.
• Safe batch processing. Every image gets its own row with a download link, the size in px and inches, DPI, file size and warnings. Images that fail are listed with the reason and are never charged.

Who it's for

Amazon Merch on Demand, Redbubble, TeePublic, Spreadshirt, Etsy + Printful/Printify sellers, KDP low-content and cover designers, and anyone with designs that are too small to print. Typical sources:

• AI art (Midjourney, DALL·E, Stable Diffusion: 1024–1536 px)
• old designs made at 72 DPI
• client logos
• Canva exports
• images saved from the web that you own the rights to

How to use

1. Paste image URLs, upload one image, or pick a key-value store with many images.
2. Choose a print target (default: Amazon Merch 4500 × 5400).
3. Run. Download the files from the Download column, or from the run's key-value store.

Input example

{
  "imageUrls": ["https://example.com/my-design.png"],
  "preset": "merch-standard",
  "fitMode": "contain",
  "anchor": "top"
}

KDP paperback cover (6 × 9 in, 300 pages, white paper → 12.926 × 9.25 in = 3878 × 2775 px PDF):

{ "imageUrls": ["https://example.com/full-wrap.jpg"], "preset": "kdp-paperback-cover",
  "kdpTrimSize": "6x9", "kdpPageCount": 300, "kdpPaperType": "white", "fitMode": "cover" }

Output example (one dataset row per image)

{
  "index": 1, "status": "success",
  "outputUrl": "https://api.apify.com/v2/key-value-stores/…/records/0001-my-design-merch-standard.png",
  "width": 4500, "height": 5400, "dpi": 300, "printWidthInches": 15, "printHeightInches": 18,
  "format": "png", "hasTransparency": true, "fileSizeMB": 3.64, "maxFileSizeMB": 25,
  "inputWidth": 1024, "inputHeight": 1229, "method": "ai", "scaleFactor": 4.43,
  "colorProfile": "sRGB IEC61966-2.1", "warnings": [], "error": null
}

Print targets

Preset	Pixels	Notes / source
merch-standard	4500 × 5400 PNG, 300 DPI, ≤ 25 MB	Amazon Merch standard t-shirt/hoodie
redbubble-tee / -premium-tee / -apparel	3873 × 4814 / 2875 × 3900 / 2400 × 3200	help.redbubble.com article 202270679
redbubble-sticker / -pillow / -home-large	2800² / 3225² / 7632 × 6480	stickers, throw pillows, duvet/tapestry/blanket
redbubble-jigsaw / -mug / -tall-mug	9075 × 6201 / 2700 × 1120 / 2700 × 1624
redbubble-clock / -coaster / -pin	2940² / 1860² / 1000²
teepublic	5000 × 5500 at 150 DPI	TeePublic "all products" size
printful-tee, printify-tee	4500 × 5400	15 × 18 in at 300 DPI (check your Printify blueprint)
print-8x10 … print-24x36, print-a4/a3/a2	2400 × 3000 … 7200 × 10800	Etsy printable wall art, JPG
kdp-ebook-cover	1600 × 2560 JPG	KDP's recommended 1.6:1
kdp-paperback-cover	computed	0.125 + trim + spine + trim + 0.125 in wide; spine = pages × 0.002252 (white / standard colour), 0.0025 (cream), 0.002347 (premium colour); 24–830 pages; PDF
custom	any W × H px, or inches × DPI	up to 16000 px per side / 120 MP
scale	×1 – ×8	keeps the aspect ratio

Platforms change their specs. Check the platform's current help page before a big batch.

How it decides what to do

• Needs ≥ 1.25× enlargement → AI. Real-ESRGAN ×4, then an exact Lanczos resize to the target. Above 6× (e.g. a 250 px logo for Merch) it runs two AI passes.
• Needs < 1.25× → a high-quality Lanczos resize. This is just as good and much faster. The image is still converted, DPI-tagged, fitted and size-limited.
• After AI → a colour-fidelity correction (back-projection), so pinks, navies and skin tones stay the colour you designed. Raw Real-ESRGAN tends to darken or tint them.

Quality (our own tests)

We drew test designs at 2000 × 2400 px, shrank them to 25 %, upscaled them back, and compared each result to the original. The higher the PSNR, the closer to the original.

Test image	Plain Lanczos	AI general (default)	AI illustration
Typography with outlines + small print	29.3 dB	36.9 dB	33.4 dB
Thin line art / mandala	24.5 dB	30.4 dB	26.9 dB
Sticker illustration, soft shadow	29.3 dB	35.2 dB	33.0 dB
Same illustration, JPEG-damaged source	28.8 dB	32.7 dB	31.3 dB
Neon glow (semi-transparent)	35.5 dB	38.1 dB	35.2 dB
Wildlife photo (NASA, public domain)	33.0 dB	32.4 dB	32.8 dB

On designs, text and line art the AI result is much sharper, with clean edges and no halos. On photos it removes JPEG blockiness and noise, but it can't invent detail that was never there. Faces and fine textures will look smooth, not "re-photographed".

Speed, memory and limits

• CPU only (Apify has no GPUs). A typical Merch job, 1024 px design → 4500 × 5400 transparent PNG, takes about 40 s at 8 GB, 100 s at 4 GB (default), 3 min at 2 GB, and 5–6 min at 1 GB. Small targets (stickers, pins) take a few seconds per image.
• Memory: 4500 × 5400 needs about 0.4 GB. The largest presets (24 × 36 in, jigsaw) need about 1 GB and are refused below 2 GB, with a clear message and no charge.
• Inputs:
  • PNG, JPG, WEBP, GIF (first frame on request), BMP, TIFF
  • max 50 MB (configurable up to 100 MB) and 50 MP
  • at least 16 px per side
• Rejected inputs (never charged): SVG/PDF inputs (export them to PNG first), HTML "share" pages instead of image links, animated images (unless you pick first frame), fully transparent images.
• Converted, with a warning: 16-bit images are reduced to 8-bit. CMYK without an embedded profile is converted with a generic formula; convert in your editor if exact colours matter.
• Hardcover KDP covers are not computed. Use KDP's cover calculator with custom.
• Rights: only upscale artwork you own or are licensed to use. Upscaling does not make an image copyright-free.

Pricing

Pay per successfully upscaled image, with platform usage included. Each image is charged exactly one of these events, never both:

Output size	Event	Price	Examples
Up to 40 megapixels	image-upscaled	$0.06	Merch 4500×5400 (24.3 MP), TeePublic 5000×5500 (27.5 MP), Printful/Printify, Redbubble tees/stickers/mugs, 8×10–18×24 in prints (18×24 = 38.9 MP), A4–A2, KDP covers
Over 40 megapixels (width × height > 40,000,000)	large-image-upscaled	$0.10	24×36 in poster at 300 DPI (7200×10800 = 77.8 MP), Redbubble duvet/tapestry (49.5 MP), jigsaw (56.3 MP)

Failed, rejected and skipped images cost nothing. Set "Maximum cost per run" and the Actor checks the right price for each image before processing it, then stops cleanly before going over your limit. Every dataset row shows pricingTier (standard/large) and chargedEvent.

Examples: 100 Merch designs = $6.00 · 1,000 sticker files = $60 · 50 posters at 24×36 in = $5.00.

Models and licenses

Option	Network	Weights	License
general (default)	Real-ESRGAN realesr-general-x4v3 (SRVGGNetCompact)	official release v0.2.5.0, github.com/xinntao/Real-ESRGAN	BSD-3-Clause
illustration	Real-ESRGAN realesr-animevideov3	official release v0.2.5.0	BSD-3-Clause

The weights were converted to ONNX without modification and run with ONNX Runtime (MIT). The BSD-3-Clause license allows commercial use and redistribution with attribution. It is included in the Actor image (models/LICENSE-Real-ESRGAN.txt). Copyright (c) 2021, Xintao Wang.

FAQ

Will Amazon accept the files? The files match Merch's published requirements: 4500 × 5400 PNG, sRGB, 300 DPI, under 25 MB. Content review is up to Amazon.

Is it a vectorizer? No. The output is a sharp raster. For logos that must scale to billboard size, use a vector tool.

Can I keep my EXIF data? Set metadata to keep. The orientation tag is reset, because the pixels are already rotated.