How to Upscale Anime and Illustration Art Without Ruining the Line Art

Anime screenshots, fan art, manga panels and digital illustrations look simple compared with photos: clean outlines, flat fills, a few soft gradients. That simplicity is exactly why they are easy to ruin when enlarged. A photo can hide a little blur or invented texture. A cel-shaded character cannot.

Why illustration is different from photos

Photos are full of fine, random texture: skin pores, leaves, noise. Upscalers trained on photos learn to add that kind of texture. Illustration has the opposite properties:

• Hard, continuous outlines that should stay one consistent width.
• Large flat areas of colour that should stay perfectly flat.
• Deliberate gradients (hair shading, skies) that should stay smooth, without banding.
• Very little natural noise, so any noise you see is usually compression damage.

Feed artwork to a photo model and you often get grainy fills, wobbly lines and a faint “painted over” texture. Feed it to simple bicubic interpolation and the lines turn soft and grey at the edges. Neither is what you want.

The usual problems in the source

Before choosing a tool, look at what is actually wrong with your image:

• JPEG artifacts. Blocky patches in flat areas and “mosquito noise” (speckles) around dark outlines. Extremely common in images saved from social media and image boards.
• Colour banding. Visible steps in gradients, often from 8-bit compression.
• Video compression. Screenshots from streams carry blockiness and smeared colour detail, especially in reds.
• Low resolution. Thumbnails and old wallpapers at 640×480 or similar.

Upscaling magnifies all of these. Dealing with the first three is half the job.

Tools built for anime and artwork

A few well-known options show the range of approaches:

• waifu2x (released in 2015) was one of the first widely used neural upscalers and was trained specifically on anime-style art. It combines upscaling with adjustable JPEG noise reduction.
• Real-ESRGAN ships with dedicated anime models in addition to its general photo model. The anime variants are tuned to keep outlines sharp and fills clean.
• Anime4K is a set of real-time shaders aimed at upscaling anime video during playback, trading some quality for speed.

Whatever tool you use, the most important choice is selecting a model trained on illustration rather than photos. IncreaseAI is being built with a separate illustration model for this reason.

Step-by-step workflow

1. Get the cleanest source

Search for the original upload or a higher-resolution version before upscaling anything. Artists often post larger files on their own portfolio pages than on social platforms. For screenshots, capture from the highest-quality stream or source available and save as PNG, not JPEG.

2. Choose the right scale

• 2× is the safest factor and usually enough for wallpapers and prints up to medium size.
• 4× works well on small, clean sources such as old 480p frames or thumbnails.
• If you need an exact size (say 3840×2160 for a 4K wallpaper), upscale past it and then downscale with Lanczos.

3. Denoise for artwork, not photos

Turn on JPEG artifact removal, but start at the lowest effective level. Too much noise reduction on artwork:

• Erases thin lines such as hair strands and eyelashes.
• Flattens deliberate textures like paper grain or screentone.
• Merges small details such as highlights in eyes.

If the source is a clean PNG, you may not need denoising at all.

4. Upscale with an illustration model

Run the upscale and compare against the original at 100% zoom. Look specifically at:

• Line weight consistency. Lines should not thicken in some places and thin out in others.
• Line endings. Tapered strokes should stay tapered, not blunt.
• Flat fills. No grain, no faint patterns.
• Eyes and small text. Highlights, pupils and lettering are where errors show first.

5. Skip most of the sharpening

Illustration models already output hard edges. Additional sharpening tends to create bright halos around dark outlines, which look especially bad against flat colours. If anything looks soft, try a different model before reaching for a sharpen filter.

6. Export as PNG (or lossless WebP)

Flat colours and hard edges are exactly what JPEG compresses worst. Export the master as PNG. For the web, lossless WebP is usually noticeably smaller than PNG with identical quality. See JPEG vs PNG vs WebP vs AVIF for the details.

Special cases

Pixel art

Pixel art is the one style where you do not want new detail. Use nearest neighbour scaling at whole-number factors (2×, 3×, 4×) to keep every pixel a crisp square. AI upscalers and smoothing filters will round off the shapes the artist placed deliberately. Dedicated pixel-art scalers exist if you want smoothed curves while keeping a hand-drawn feel, but they are a stylistic choice rather than a restoration.

Manga and screentone

Black-and-white manga uses halftone dot patterns (screentone) for shading. Strong denoising reads those dots as noise and blurs them into grey, while some models turn them into moiré. Use minimal denoise and inspect toned areas carefully. Converting to greyscale before upscaling can help avoid colour fringing on scans.

Line art you plan to colour

If you are going to colour or edit the art, consider vectorising clean line art instead of upscaling it. Vector paths scale to any size without any loss. This works best on bold, clean lines and poorly on sketchy or textured art.

Respect the artist

Upscaling someone else’s artwork does not change who owns it. Upscaling for a personal wallpaper is one thing; reposting or selling an upscaled version usually needs the artist’s permission. Credit the original and link to it when you share.

Quick checklist

1. Find the largest, least-compressed original.
2. Use a model trained on anime or illustration.
3. Denoise lightly, only as much as the JPEG damage requires.
4. Prefer 2×; use 4× on small, clean sources.
5. Check lines, fills and eyes at 100%.
6. Skip extra sharpening.
7. Save as PNG or lossless WebP.

For a broader look at upscaling, read how to increase image resolution without losing quality. IncreaseAI is being built with a dedicated illustration model and lossless export, with a free tier planned for small images.