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Upscale Image and Upscale Image By node in ComfyUI

Upscale Image (ImageScale) and Upscale Image By resize an IMAGE with classic interpolation (nearest, bilinear, bicubic, lanczos, area) to an exact size or by a factor, with no AI model involved.
Node pack: ComfyUI core
Category: Upscaling

What Upscale Image and Upscale Image By does

These two nodes are plain resizers. Upscale Image takes a target width and height plus a crop option (disabled or center); Upscale Image By takes a scale factor. The upscale_method choices are the usual filters: nearest-exact for pixel art, bilinear and bicubic for smooth results, lanczos for the sharpest classic scaling, area for downscaling without aliasing.
Despite the name they are just as useful for shrinking: downscale a 4K photo before VAE Encode, or bring the output of a 4x AI upscaler back to 2x. For real detail gain, pair Upscale Image Using Model with these nodes, or use Upscale Latent for a hires pass.

Inputs

Name
Type
What it is
image
IMAGE
The picture to resize.
upscale_method
COMBO
nearest-exact, bilinear, area, bicubic or lanczos.
width / height (Upscale Image)
INT
Target size in pixels; 0 keeps the aspect ratio from the other side.
crop (Upscale Image)
COMBO
disabled stretches, center keeps the aspect ratio and crops.
scale_by (Upscale Image By)
FLOAT
Factor, 0.5 halves, 2.0 doubles.

Outputs

Name
Type
What it is
IMAGE
IMAGE
The resized picture.
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How to use Upscale Image and Upscale Image By

  1. Add Upscale Image By after the picture you want to resize.
  2. Pick lanczos for photos, nearest-exact for pixel art.
  3. Set scale_by (0.5 to halve a 4x upscaler result, 2.0 to double).
  4. Connect the result to the next node (VAE Encode for a second pass, Save Image to keep it).
  5. Use Upscale Image with crop center to make an input exactly 1024x1024.

Settings and tips

  • Setting width or height to 0 in Upscale Image keeps the aspect ratio.
  • A 4x ESRGAN model followed by Upscale Image By 0.5 gives a clean 2x with fewer artefacts than a 2x model on some pictures.
  • Sizes must be multiples of 8 before VAE Encode; 1024, 1152, 1344 are safe.
  • area is the best method for downscaling; lanczos for upscaling.

Troubleshooting Upscale Image and Upscale Image By

The result is blurry

Why it happens
Interpolation cannot invent detail; a 2x bicubic upscale is a smooth enlargement.

How to fix it
Use Upscale Image Using Model with an ESRGAN model, or a hires pass through the sampler, then resize.

The picture is squashed

Why it happens
Upscale Image with crop disabled and a width/height that do not match the source ratio.

How to fix it
Set one side to 0, or set crop to center.

VAE Encode fails after resizing

Why it happens
The new size is not a multiple of 8.

How to fix it
Choose multiples of 8 (or 64 for SDXL best results).

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Questions about Upscale Image and Upscale Image By

Which method is best?

lanczos for upscaling photos and renders, area for downscaling, nearest-exact for pixel art.

Does this use the GPU?

Yes, torch interpolation runs on the GPU and is nearly instant.

Related nodes

Upscale Image (using Model)
ComfyUI core
Upscale Image (using Model) runs an ESRGAN-style upscaler (4x-UltraSharp, RealESRGAN, 4x_NMKD-Siax, 4x_foolhardy_Remacri) over an IMAGE and returns it enlarged by the model's fixed factor with added detail.
Upscale Latent and Upscale Latent By
ComfyUI core
Upscale Latent resizes a latent to a new size (or by a factor) so a second KSampler can add detail at higher resolution: the classic hires fix.
Ultimate SD Upscale
ComfyUI_UltimateSDUpscale
Ultimate SD Upscale enlarges a picture with an ESRGAN model, then re-samples it tile by tile through the diffusion model with your prompt at low denoise, adding real detail at 2x-4x without running out of VRAM.
VAE Encode and VAE Encode (for Inpainting)
ComfyUI core
VAE Encode converts a pixel IMAGE into a LATENT for img2img; VAE Encode (for Inpainting) does the same while blanking the masked area so an inpainting model can repaint it.
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