Output and image quality

Output formats

saveFormat	Native result	Web result	Best for
ImageFormat.jpg	Cache-file path	JPEG data URL	Photos and smaller files
ImageFormat.png	Cache-file path	PNG data URL	Transparency, QR codes, icons, and sharp edges
ImageFormat.base64	PNG data URL	PNG data URL	In-memory transfer when you explicitly need base64

JPEG is the compatibility default. Set the format explicitly when output behavior matters.

const result = await Marker.markImage({
  backgroundImage: { src: require('./background.png') },
  watermarkImages: [
    {
      src: require('./logo.png'),
      trimTransparentPadding: true,
    },
  ],
  filename: 'marked-photo',
  saveFormat: ImageFormat.png,
});

Quality

quality accepts an integer from 0–100, where 100 is the highest quality. It has the most visible effect on JPEG because PNG output is lossless. Browser and native JPEG encoders can produce different bytes and file sizes for the same value.

For QR codes, barcodes, pixel art, and line-art logos, choose PNG. JPEG compression can soften hard edges even at high quality.

JPEG and transparency

JPEG has no alpha channel. When transparent pixels are saved as JPEG, matteColor selects the solid color placed behind them. The default is white.

saveFormat: ImageFormat.jpg,
quality: 92,
matteColor: '#FFFFFF',

Tip

Use PNG when the final image itself must remain transparent.

Rotated backgrounds

The default RotationCanvasMode.expand grows the output canvas so the full rotated image remains visible. Choose crop to keep the original canvas size and clip content outside it.

backgroundImage: {
  src: require('./background.jpg'),
  rotate: 30,
},
rotationCanvasMode: RotationCanvasMode.crop,

Filenames and storage

On native targets, the returned JPEG or PNG lives in the app’s cache directory. filename must be a safe basename, not a directory path. A supplied .jpg, .jpeg, or .png suffix is normalized to match saveFormat.

Cache output does not automatically appear in the photo library. Pass the returned path to your preferred media-library or file-system package when you need a permanent copy.

Web does not write a cache file: it returns a data URL and does not use filename. Set an anchor’s download attribute or use your own browser file workflow when saving it.

Data URLs keep more image data in JavaScript memory. This applies to every Web output and native base64 output, so avoid unnecessarily large source images.