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# Image Buffer Chroma Location Constants

Constants that indicate locations for chroma samples in the image buffer.

## Discussion

For progressive-scan image data, use the [`kCVImageBufferChromaLocationTopFieldKey`](/documentation/CoreVideo/kCVImageBufferChromaLocationTopFieldKey) key to attach one of these values to the image buffer. For interlaced image data, attach values to the image buffer using the [`kCVImageBufferChromaLocationTopFieldKey`](/documentation/CoreVideo/kCVImageBufferChromaLocationTopFieldKey) and [`kCVImageBufferChromaLocationBottomFieldKey`](/documentation/CoreVideo/kCVImageBufferChromaLocationBottomFieldKey) keys.

## Topics

### Constants

[`let kCVImageBufferChromaLocation_Left: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_Left)

A key that indicates the chroma sample is horizontally co-sited with the left column of luma samples, but centered vertically.

[`let kCVImageBufferChromaLocation_Center: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_Center)

A key that indicates the chroma sample is fully centered.

[`let kCVImageBufferChromaLocation_TopLeft: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_TopLeft)

A key that indicates the chroma sample is co-sited with the top-left luma sample.

[`let kCVImageBufferChromaLocation_Top: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_Top)

A key that indicates the chroma sample is horizontally centered, but is co-sited with the top row of luma samples.

[`let kCVImageBufferChromaLocation_BottomLeft: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_BottomLeft)

A key that indicates the chroma sample is co-sited with the bottom-left luma sample.

[`let kCVImageBufferChromaLocation_Bottom: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_Bottom)

A key that indicates the chroma sample is horizontally centered, but is co-sited with the bottom row of luma samples.

[`let kCVImageBufferChromaLocation_DV420: CFString`](/documentation/CoreVideo/kCVImageBufferChromaLocation_DV420)

A key that indicates the Cr and Cb samples are alternatingly co-sited with the left luma samples of the same field.


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