Resize

Adjust the dimensions of images stored in OSS in real-time, without downloading and processing locally. Supports proportional scaling, fixed-size scaling, long/short edge control, and multiple scaling modes.

Function

Operation: resize
URL pattern: ?x-oss-process=image/resize,{param}_{value}[,...]
Supports proportional scaling (p) and fixed-size scaling (w/h)
Provides 5 scaling modes (lfit/mfit/fill/pad/fixed)
Supports long/short edge control (l/s) and enlargement limiting (limit)

Parameters

Param	Type	Required	Default	Range	Description
`m`	String	No	`lfit`	See table below	Scaling mode
`w`	Integer	No	—	`[1, 16384]` (px)	Target width
`h`	Integer	No	—	`[1, 16384]` (px)	Target height
`l`	Integer	No	—	`[1, 16384]` (px)	Target long-edge length
`s`	Integer	No	—	`[1, 16384]` (px)	Target short-edge length
`p`	Integer	No	—	`[1, 1000]` (%)	Proportional scaling percentage
`limit`	Integer	No	`1`	`0` / `1`	`1`:return original if target exceeds source;`0`:allow enlargement
`color`	String	No	`FFFFFF`	6-digit RGB hex	Fill color for `pad` mode

Scaling modes (m)

Example: source 200×100 px, target 150×80 px:

Mode	Description	Output size
`lfit`	Proportional scale, largest image fitting within w×h	150×75 px
`mfit`	Proportional scale, smallest image covering w×h	160×80 px
`fill`	Based on `mfit`, excess cropped at center	150×80 px
`pad`	Based on `lfit`, blank filled with color	150×80 px
`fixed`	Fixed w×h forced scaling, may distort	150×80 px

[!NOTE]

When only w or h is specified, lfit/mfit/fixed scale proportionally; pad/fill force square

When w or h is set, l and s have no effect

p is mutually exclusive with w/h/l/s; w/h/l/s take precedence

Code Examples

URL DSL

# Proportional scale to 50%
?x-oss-process=image/resize,p_50

# Width 200px, height auto
?x-oss-process=image/resize,w_200

# Fixed 100×100, center-crop mode
?x-oss-process=image/resize,m_fill,w_100,h_100

processImage (URL string)

import { processImage } from '@imgx-kit/core';

const buf = await processImage(
  './photo.jpg',
  'image/resize,p_50',
);

imgx chain API

import { imgx } from '@imgx-kit/core';

// Proportional scale to 50%
const buf1 = await imgx('./photo.jpg')
  .resize({ p: 50 })
  .toBuffer();

// Width 200
const buf2 = await imgx('./photo.jpg')
  .resize({ w: 200 })
  .toBuffer();

// Fixed 100×100 center-crop
const buf3 = await imgx('./photo.jpg')
  .resize({ m: 'fill', w: 100, h: 100 })
  .toBuffer();

Edge Cases & Limits

Source limits: ≤ 20 MB, side ≤ 30,000 px, total pixels ≤ 250 M
Output limits: side ≤ 16,384 px, total pixels ≤ 16,777,216
Animated images (e.g., GIF) count pixels as width × height × frames
Animated images do not support p, only w/h reduction, no enlargement
With limit_1, target larger than source returns original resolution
General size / pixel limits: see Getting Started