---
title: kCGImagePropertyPNGCompressionFilter
framework: imageio
role: symbol
role_heading: Global Variable
path: imageio/kcgimagepropertypngcompressionfilter
---

# kCGImagePropertyPNGCompressionFilter

The PNG filter to apply prior to compression.

## Declaration

```swift
let kCGImagePropertyPNGCompressionFilter: CFString
```

## Discussion

Discussion The value of this key is a CFNumber. The number contains a bitwise-OR of one or more filter constants, such as IMAGEIO_PNG_FILTER_AVG or IMAGEIO_PNG_FILTER_SUB. The value has no effect on formats other than PNG.

## See Also

### Pre-Compression Filters

- [IMAGEIO_PNG_NO_FILTERS](imageio/imageio_png_no_filters.md)
- [IMAGEIO_PNG_FILTER_NONE](imageio/imageio_png_filter_none.md)
- [IMAGEIO_PNG_FILTER_SUB](imageio/imageio_png_filter_sub.md)
- [IMAGEIO_PNG_FILTER_UP](imageio/imageio_png_filter_up.md)
- [IMAGEIO_PNG_FILTER_AVG](imageio/imageio_png_filter_avg.md)
- [IMAGEIO_PNG_FILTER_PAETH](imageio/imageio_png_filter_paeth.md)