subsampleFactor
The factor by which to scale down a returned images.
Declaration
static let subsampleFactor: CIImageOptionDiscussion
The value of this key should be an NSNumber containing the integer value 2, 4, or 8. It can be used to improve performance and reduce memory usage when working with large images.
When you specify this key, the retured image will be scaled down the image data by the specified numerical factor. If the image format doesn’t support the specified scale factor, a larger or full-size normal image is returned.
This option is only supported by JPEG, HEIF, TIFF, PNG and RAW images formats.
This option is only supported by these APIs:
/CIImage/imageWithContentsOfURL:options:/CIImage/initWithContentsOfURL:options:/CIImage/imageWithData:options:/CIImage/initWithData:options:/CIImage/imageWithCGImageSource:index:options:/CIImage/initWithCGImageSource:index:options: