---
title: kCGImageSourceSubsampleFactor
framework: imageio
role: symbol
role_heading: Global Variable
path: imageio/kcgimagesourcesubsamplefactor
---

# kCGImageSourceSubsampleFactor

The factor by which to scale down any returned images.

## Declaration

```swift
let kCGImageSourceSubsampleFactor: CFString
```

## Discussion

Discussion When you specify this key, the image source scales down the image data by the specified numerical factor. The value of this key must be a CFNumber containing the integer value 2, 4, or 8. If the image doesn’t support the specified scale factor, the image source provides a larger or full-size normal image. Image sources support this option only for JPEG, HEIF, TIFF, and PNG images.

## See Also

### Specifying the Read Options

- [kCGImageSourceTypeIdentifierHint](imageio/kcgimagesourcetypeidentifierhint.md)
- [kCGImageSourceShouldAllowFloat](imageio/kcgimagesourceshouldallowfloat.md)
- [kCGImageSourceShouldCache](imageio/kcgimagesourceshouldcache.md)
- [kCGImageSourceShouldCacheImmediately](imageio/kcgimagesourceshouldcacheimmediately.md)
- [kCGImageSourceCreateThumbnailFromImageIfAbsent](imageio/kcgimagesourcecreatethumbnailfromimageifabsent.md)
- [kCGImageSourceCreateThumbnailFromImageAlways](imageio/kcgimagesourcecreatethumbnailfromimagealways.md)
- [kCGImageSourceThumbnailMaxPixelSize](imageio/kcgimagesourcethumbnailmaxpixelsize.md)
- [kCGImageSourceCreateThumbnailWithTransform](imageio/kcgimagesourcecreatethumbnailwithtransform.md)