Quality

Adjust image compression quality in real-time to achieve the best balance between visual quality and file size.

Function

  • Operation: quality
  • URL pattern: ?x-oss-process=image/quality,{param}_{value}
  • Supports relative quality (q) and absolute quality (Q)
  • Only effective for JPG / WebP; PNG / GIF and other lossless formats unaffected
  • Q takes precedence when both q and Q are present

Parameters

ParamTypeRequiredDefaultRangeDescription
qIntegerNo—[1, 100] (%)Relative quality: compress as % of source quality
QIntegerNo—[1, 100] (%)Absolute quality: directly specify target quality

[!NOTE]

  • q relative quality: source 80%, q_90 outputs 72% (80% × 90%)
  • Q absolute quality: compresses to target if source ≥ target; keeps source if source < target
  • For JPG, q is relative; for WebP, q behaves like Q (absolute)
  • When both q and Q are present, Q takes precedence

Code Examples

URL DSL

# Relative quality 90%
?x-oss-process=image/quality,q_90

# Absolute quality 75%
?x-oss-process=image/quality,Q_75

processImage (URL string)

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

const buf = await processImage(
  './photo.jpg',
  'image/quality,q_90',
);

imgx chain API

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

// Relative quality
const buf1 = await imgx('./photo.jpg')
  .quality({ q: 90 })
  .toBuffer();

// Absolute quality
const buf2 = await imgx('./photo.jpg')
  .quality({ Q: 75 })
  .toBuffer();

Edge Cases & Limits

  • Only effective for JPG / WebP
  • PNG / GIF and other lossless formats are unaffected
  • Q takes precedence when both q and Q are present
  • General size / pixel limits: see Getting Started